VATICAN CITY (AP) — More than 130 Catholic cardinals on Wednesday began the secretive, centuries-old ritual to elect a successor to Pope Francis, opening the most geographically diverse conclave in the faith’s 2,000-year history.

Two by two, the cardinals entered the Sistine Chapel chanting the meditative “Litany of the Saints” as Swiss Guards stood at attention. The hymn implores the saints to help the cardinals find a new leader of the 1.4 billion-strong Catholic Church. They bowed before the altar and took their places before taking an oath of secrecy and shutting the Sistine Chapel doors to start the conclave.

Here is the latest:

Security checks at St. Peter’s Square

Those hoping to witness the election of the next pope from St. Peter’s Square must first pass through security checks.

As the conclave began, lines were forming at metal detectors at the square’s entrances. Once a new pope is elected, he’ll appear on the balcony above the square to be introduced to the world.

For now, the checks remain relatively quick, but wait times are expected to grow once the white smoke appears. Italy’s Civil Protection agency estimates that up to 250,000 people could flood the square and Via della Conciliazione, the wide boulevard that leads from the Vatican to the Tiber River, to welcome the new pontiff.

Sense of expectation is building ahead of ‘historic moment’

Crowds were filling St. Peter’s Square as cardinals prepared to elect the next pope.

People from all faiths are captivated by the ancient ritual playing out. But the sense of meaning is obviously most profound for Catholic believers.

Father Ignacio Palacios, a professor and priest in the diocese of Toledo, Spain, took part in a Mass in St. Peter’s Basilica ahead of the conclave and observed others taking photos with cardinals — especially with those seen as having the best chances to emerge from the conclave as pope.

He described a “a strong sense of expectation.”

“It’s nice to feel this strong sense of faith and belonging,” he said. “We are aware of the fact that we are witnessing a historic moment.”

Cardinals electing the next pope begin processing into the Sistine Chapel to open the conclave

As they processed into the chapel adorned with Michelangelo’s “The Last Judgement,” the 133 cardinals chanted the meditative “Litany of the Saints.” A line of Swiss Guards stood at attention.

The hymn implores the saints to help the cardinals find a new leader of the 1.4 billion-strong Catholic Church.

Cardinals are preparing to enter the Sistine Chapel. Here’s what will happen inside

At 4:30 p.m. (1430 GMT; 10:30 a.m. EDT), the cardinals will walk into the Sistine Chapel, chanting the meditative “Litany of the Saints” and the Latin hymn “Veni Creator,” imploring the saints and the Holy Spirit to help them pick a pope.

Once there, they pledge to maintain secrecy about what’s about to transpire and to not allow any interference from outsiders to influence their voting.

Standing before Michelangelo’s vision of heaven and hell in “The Last Judgment,” each cardinal places his hand on the Gospel and swears to carry out that duty. The awesomeness of the chapel’s frescoes, and Michelangelo’s in particular, is meant to remind the cardinals of the weighty responsibility they bear.

After the cardinals take their oaths, a senior cardinal delivers a meditation. The master of papal liturgical ceremonies, Archbishop Diego Ravelli, calls out “Extra omnes,” Latin for “all out.” Anyone not eligible to vote then leaves and the chapel doors close, allowing the work to begin.

Kenyan Cardinal John Njue confirms he’s not participating in the conclave

He cited poor health but also insisted he never received an invitation to attend.

The former head of the Catholic Church in Kenya found himself at the center of controversy this week after the local newspaper Daily Nation quoted him as saying he hadn’t received an invitation to attend. The Vatican had said Njue wouldn’t be participating due to health issues, one of two cardinals under age 80 who didn’t come to Rome to participate.

Cardinals who are eligible to vote in a conclave don’t need an invitation, but they usually receive a formal communication announcing the conclave’s date and procedures.

Njue told The Associated Press he hadn’t received any letter indicating he needed to attend. But he also gave poor health as another reason for staying home.

The current archbishop of Nairobi, Archbishop Philip Anyolo, said earlier this week that Njue had been invited but wouldn’t attend due to poor health. Anyolo said in a statement that the official invitation had been received through the Vatican’s embassy in Nairobi.

‘A woman’s place is in the conclave’

A group of women lit pink smoke flares on a hill behind the Vatican on Wednesday in protest against the male-dominated Catholic church just hours before 133 men gather in the Sistine Chapel to choose the next pope.

“While the world may be waiting for white or black smoke, our pink smoke is a signal that women should be included in every aspect of the life of the Church,” said Kate McElwee, executive cirector of Women’s Ordination Conference, adding, “A woman’s place is in the conclave.”

The women said they have been arrested in the past when they have brought their protests closer to St. Peter’s Square so they were holding their pink smoke event on the Ganicolo Hill behind the Vatican with the cupola on St. Peter’s Basilica visible in the distance.

A cardinal by any other name

As the cardinals prepare for the start of the conclave, many wonder if the next pontiff's name will be Petrus, Robertus or Ioannes? Maybe Claudius or Christophorus? Or perhaps Timoteus?

The crowds should be prepared to hear it first not in a cardinal's native Italian, French, Spanish or other tongue, but in Latin.

The new pope will be announced with the Latin proclamation: “Annuntio vobis gaudium magnum: Habemus Papam!” (“I bring you tidings of great joy: We have a pope!”)

That will be immediately followed by the revelation of his birth name, in Latin, followed by the papal name he has chosen, also in Latin.

If the first word uttered is Petrus, that could refer to several cardinals whose names are some version of Peter, including Pietro Parolin, Peter Turkson and Péter Erdő. Also, several of the cardinals' names include some version of Ioannes, or John.

Mass ahead of the start of the conclave is over

A morning Mass in St. Peter’s Basilica has concluded, allowing the cardinals who will elect the next pope to return to their residences for a few hours ahead of the conclave.

Later in the afternoon, the Vatican has said that all communications around the Holy See will be jammed as they prepare to withdraw from the outside world for their secret and sacred task ahead.

The cardinals are likely to cast their first vote later on Wednesday. Assuming no one is elected, black smoke would be expected out of the Sistine Chapel chimney at around 7 p.m.

The cardinals will then retire for the night and return on Thursday morning. They can hold up to two ballots in the morning and two in the afternoon until a winner is found.

While cardinals this week said they expected a short conclave, it will likely take at least a few rounds of voting.

A prayer for a young pope

Lisette Herrera, a 54-year-old tourist from the Dominican Republic, was deeply moved to find herself by chance in the heart of Roman Catholicism as the church plans to select a new pope.

On Wednesday morning, she decided to skip seeing the Spanish Steps and the Trevi Fountain and other sites to pray in St. Peter’s Square and wait for a new pope, even though she realizes there is no telling how long the conclave could take.

“I’m praying the Holy Spirit for a young pope who would stay with us for a long time,” she said. “I don’t believe in conclave politics, I just feel that the Holy Spirit is here and that’s all we need to know.”

Rome on high alert ahead of the conclave

The Vatican’s Swiss Guards and Italian carabinieri and police have been mobilized as Rome and the wider world hold their breath to see who will emerge from the conclave as the next pontiff.

As of Wednesday morning, when cardinals attended a special pre-conclave Mass in St. Peter’s Basilica, police were carrying out enhanced checks of people entering St. Peter’s Square.

Over 4,000 officers have been deployed, with an anti-drone system and signal jammers to block communication between the cardinals and the outside world once they enter into their secret assembly.

“The safety of the cardinals is a priority, but so is that of the faithful outside,” said Fabio Ciciliano, head Italy’s Civil Protection agency.

A please to choose a pope who prizes unity in diversity

A senior cardinal has urged the cardinals who will vote in the conclave to elect a pope who prizes unity in diversity, and puts personal interests aside.

Cardinal Giovanni Battista Re, the dean of the College of Cardinals, outlined the marching orders for the 133 men who will enter the Sistine Chapel later on Wednesday to begin voting to elect a new pope.

In his sermon at the final pre-conclave Mass at St. Peter's Basilica, Re reminded the cardinals that a conclave represented the highest human and church responsibility, and that they must set aside “every personal consideration.”

He said the new pope should foster communion and unity within the church.

A final pre-conclave Mass

Cardinals have entered St. Peter’s Basilica on Wednesday to celebrate the final Mass before the conclave to elect a new pope.

The dean of the College of Cardinals, Giovanni Battista Re, is celebrating the Mass and leading the prayers for cardinals to find the wisdom, counsel and understanding to choose a worthy new shepherd.

Re, 91, had presided at Francis’ funeral two weeks ago, delivering a heartfelt sermon recalling history’s first Latin American pope and the reforming 12-year papacy he oversaw.

Later in the day, the cardinals will sequester themselves in the Sistine Chapel to begin casting their ballots.

How the voting works

The electors cast paper ballots, and voting continues until one candidate receives a two-thirds majority, or 89 votes. After two rounds of voting, ballots are burned in a special stove — black smoke signals no decision, while white smoke means a new pope has been chosen.

The last few popes have been elected within a few days, but there is no formal deadline. Electors must be under 80, and are more geographically diverse than ever.

They represent Catholicism’s growing presence in Africa, Asia and Latin America, as well as its traditional power base in Europe.

Prayers in the Philippines for another pope good for poor people

Nearly 100 people in a slum in Manila, the Philippine capital, were praying Wednesday for the conclave to elect another pope who will reach out to the poor.

Rev. Robert Reyes told the crowd in a small chapel surrounded by shanties in suburban Quezon city that the next pope should be humble and inclusive, like Francis.

“Francis was such a unique person open to all, specially to those who are neglected, forgotten, marginalized, rejected and oppressed,” said Reyes.

The Philippines, the largest Roman Catholic nation in Asia, has long been plagued by poverty and inequality.