The blast occurred at 9:30 a.m. Friday in a mine in Panzhihua, a city in Sichuan province, according to the Xinhua News agency. No other miners were injured and none were missing, according to the director of safety for Panzhihua, Wang.
The seven killed were the only ones working in the mine at the time of the accident, Xinhua said.
Though the mine had all required operating licenses, the pit had been closed down before the accident, but the contractor reportedly neglected the official order and resumed operation without authorization.
The boss of the coal pit and two employees responsible for safety inspections were arrested, and police were searching Sunday for the contractor, who Wang said had fled. Investigators hadn't determined what caused the explosion.