BEIJING (AP) — A gas explosion at a coal mine in China’s northern province of Shanxi killed at least 90 people, state media reported Saturday.

Official news agency Xinhua said the accident at Changzhi city’s Liushenyu coal mine happened on Friday evening. Around 247 workers were on duty at the time.

The agency initially reported early Saturday eight people were killed and 38 were trapped underground. Nine were still trapped as of Saturday afternoon, Xinhua said.

The cause of the explosion was under investigation, Xinhua reported, and rescue work is pressing on. Among the injured, many were hurt by toxic gas, according to state media CCTV.

Chinese President Xi Jinping has called for an all-out effort to rescue the missing and an investigation of the accident's cause while holding those responsible accountable, reported Xinhua.

Shanxi province is known as China’s main coal mining province. With a size larger than Greece and a population of around 34 million, the province's hundreds of thousands of miners dug 1.3 billion tons (1.17 billion metric tons) of coal last year, or almost a third of China’s total.