BEIJING (AP) — A gas explosion at a coal mine in China’s northern Shanxi province killed at least 90 people, state media said on Saturday, in the country’s deadliest mining accident in recent years.

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.

Nine miners were still unaccounted for as of Saturday afternoon, Xinhua said, and more than 120 people were hospitalized.

The cause of the explosion was under investigation, Xinhua reported, and rescue work is pressing on with hundreds of rescuers and medical personnel sent to the site. 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, reported Xinhua.