At least 33 people died in a gas explosion in China's Jinshangou Coal Mine in Yongchuan District, The Global Times reported on Wednesday. More than 80 members of the rescue operation retrieved the bodies of 15 missing miners on Wednesday morning.

Officials said an investigation, monitored by the State Administration of Work Safety, is underway, the Chinese daily reported. The mine is a privately-owned enterprise, according to CNN.

A total of 35 miners were working in the pit at around 11.30 am on Monday when the incident occurred. Two of them managed to escape the blast. Rescue workers retrieved 18 of the bodies by Tuesday.

Officials said an initial investigation has revealed that mining activity there had exceeded the permissible boundaries and that the working conditions were very poor. The report said the pit had "insufficient and malfunctioning equipment, poor ventilation and disorderly management".