JAKARTA, Indonesia (AP) — An explosive eruption Friday of Mount Dukono on the remote Indonesian island Halmahera killed three hikers and injured five who were climbing in a restricted area around the active volcano, authorities said.

About 20 climbers had set out Thursday to ascend the nearly 1,355-meter (4,445-foot) volcano in defiance of safety restrictions, said North Halmahera police chief Erlichson Pasaribu.

They became stranded when Dukono erupted at 7:41 a.m. local time, spewing a thick ash column that rose about 10 kilometers (6 miles) above the summit. The eruption was recorded on seismographs for more than 16 minutes, Indonesia’s Geological Agency said.

“They were aware that climbing was prohibited as the mountain is a restricted zone due to its high alert status, but insisted on going ahead,” Pasaribu said in a television interview.

Rescue teams were deployed after receiving an emergency signal from the mountain area. Two Singaporean men and one Indonesian woman died at the scene, Pasaribu said.

As of Friday afternoon, 17 climbers had been safely evacuated, including seven Singaporean nationals and two Indonesians who joined the rescue operation and provided information on climbing routes of the victims before the eruption, National Disaster Management Agency spokesperson Abdul Muhari said. Five of those evacuated were reported injured.

The bodies had not yet been recovered because continued eruptions and dangerous conditions prevented rescue teams from reaching the location.

Muhari said the search and rescue operation was halted late Friday due to darkness, and would resume early Saturday.

The Center for Volcanology and Geological Hazard Mitigation has long banned activities within a 4‑kilometer (2.5‑mile) danger zone radius of Dukono’s crater, citing hazards such as volcanic explosions, ashfall and toxic gases. Officials believe the hikers were inside the restricted zone at the time of the eruption.

Despite warnings on social media and signs at the site, “many people remain determined to climb, driven by the desire to create online content,” Pasaribu said.

Mount Dukono is one of Indonesia’s most active volcanoes and has been erupting almost continuously since 1933. Indonesia sits along the Pacific “Ring of Fire,” an area of intense seismic and volcanic activity, and is home to more than 120 active volcanoes.

Authorities also have warned of possible secondary hazards, including volcanic mudflows, especially during heavy rain, which could travel along rivers flowing from the volcano’s slopes.

Volcanic activity at Dukono remains high, and authorities said it was at the second highest alert level. Authorities said the volcano has shown an increase in explosive magmatic eruptions since late March, with an average of about 95 eruptions a day.

“Friday’s eruption was among the strongest during this period,” said Lana Saria, who heads Indonesia's Geology Agency at the Energy and Mineral Resources Ministry. She added that ash clouds ranging from white to gray and black in color were being blown northward.

She warned that ashfall could affect nearby settlements, including the town of Tobelo, raising health risks and disrupting transportation and daily life.

Officials urged residents, tourists and climbers to remain calm, follow official guidance and avoid restricted areas as monitoring of Mount Dukono continues.