CHONGQING -- Punishments have been delivered to 31 people involved in a coal mine explosion that killed 22 workers, authorities in Southwest China's Chongqing municipality said.

Chongqing's coal mine safety watchdog found human error played a part in the Yanshitai coal mine explosion that occurred last June in the Wansheng economic development district, according to a press statement made by the watchdog on Friday.

The mine's owner and chief engineer are being investigated for criminal accountability, the safety watchdog said.

The prosecutors are also investigating two officials who were in charge of safety regulation in Wansheng area. The other 27 received Party or administrative penalties.