The mine was under maintenance and there was no production when the accident occurred, a representative of Xinglong coal mine in Chenzhou told Reuters, adding that a plank broke during the overhaul, which caused a gas outburst.

The representative further said that the mine, with a capacity of 150,000 tonnes per year, has been shut down and a timeline to restart production remains unknown.

The coal mine was found to have a safety violation by local government in November 2018 and was fined 10,000 yua.