An explosion in a coal mine in northern China has killed at least 82 people, with some still unaccounted for, state media say. President Xi Jinping has demanded an "all-out" effort to search for and rescue those missing.

At least 82 people have died after a gas explosion at a coal mine in northern China, state media reported on Saturday.

Rescuers were still searching "intensively" for nine people who remained unaccounted for, according to state news agency Xinhua.

The blast took place at 7:29 pm (1129 GMT/UTC) on Friday at the Liushenyu coal mine in Qinyuan county in Shanxi, one of China's poorer provinces, with 247 ⁠workers ​on duty ​underground, Xinhua said

Xinhua reported that most had been brought safely to ​the surface by early Saturday.

What Else Do We Know about the Chinese Coal Mine Accident?

Earlier, Xinhua said that levels of carbon monoxide had "exceeded limits" at the mine. Some of those trapped underground were in "critical condition," it said.

Chinese President Xi Jinping urged authorities to "spare no ‌effort" in treating the injured and conducting ‌search ​and rescue operations, according to Xinhua.

Xi also ordered a thorough investigation into the cause of the accident and strict ​accountability in accordance with the law.

He stressed that "all regions and departments must draw lessons from this accident, remain constantly vigilant regarding workplace safety ... and resolutely prevent and curb the occurrence of major and catastrophic accidents."

In recent decades, mine safety in China has improved, but accidents are still frequent in an industry where safety protocols are often lax.