At least 90 ​people were killed in a gas explosion at a coal ‌mine in China’s northern province of Shanxi, the country’s deadliest mining accident since at least 2009.

The gas explosion occurred late on Friday at the Liushenyu ​coal mine in Qinyuan county, with 247 workers on duty ​underground, state media Xinhua reported.

The mine is operated by Shanxi Tongzhou Group Liushenyu Coal Industry, which was established in 2010 ​and is controlled by Shanxi Tongzhou Coal Coking Group, according to ​corporate database Qichacha.

Rescue operations were ongoing, and the cause of the accident was under investigation, according to the local emergency management authority in Qinyuan. Shanxi is ​China’s coal-mining heartland.

President Xi Jinping called for authorities to “spare no ​effort” in treating the injured and conducting search and rescue operations, while ordering a ‌thorough investigation into the cause of the accident and strict accountability in accordance with the law, according to Xinhua.

Premier Li Qiang called for the timely and accurate release of information and rigorous accountability.

China has significantly ​reduced coal mine ​fatalities - often caused by gas explosions or flooding - since the early 2000s through more stringent regulations and safer practices.

In ​2009, a coal and gas outburst in Heilongjiang Province ​killed 108 people and injured 133.

Executives of the company responsible for the mine have been detained, Xinhua reported.

Shanxi provincial authorities have dispatched seven rescue and medical ​teams totalling 755 personnel to the ​site, the emergency management bureau at Qinyuan said.