BEIJING (Reuters) - An explosion on Wednesday at a small coal mine in China’s Hunan province that killed two workers while another three are missing, the Hunan coal mine safety regulation bureau said.

The incident occurred at Hunan Baodian Qunli Coal Mining Co, which produces 120,000 tonnes of coal annually.

Hunan’s mine safety regulator said in a separate statement in September that it temporarily halted production at Baodian Qunli mine after finding the did not follow safety standards and its production license had expired.

It is not clear whether Baodian Qunli had a production license when the explosion occurred. The accident happened at 3 a.m. on Wednesday, the safety bureau said.

The cause of the accident is under investigation, said the municipal government of Shaoyang, the city near where the mine is located.

The coal mine is owned by Hunan Baodian Group, which is 40 percent owned by the municipal asset manager for the city of Shaoyang with China Guodian Group holding the rest. Guodian has made several attempts to sell its stake in the coal mine to private investors since 2014, according to filings with the Shanghai United Assets and Equity Exchange, a state-owned assets auction house.

The explosion is the first major coal mine accident this year and might lead to tighter scrutiny on coal mine safety practices.

China’s coal production in March fell to its lowest since October, data from the National Bureau of Statistic showed, as miners in the world’s top consumer of the fuel scaled back operations amid falling prices.