BEIJING -- A gas explosion killed two miners and trapped 23 others at a coal mine in northeast China, state media said early Tuesday.

The accident happened at Baijiagou Coal Mine in Faku County, Liaoning Province, at 8:50am (0050 GMT) Monday, state Xinhua news agency said, quoting a provincial coal mine safety bureau official.

Updating earlier figures, the agency quoted the official as saying 14 miners were brought out of the pit mid-afternoon and rushed to hospital but two died despite doctors' efforts.

An operation to rescue the 23 still trapped was ongoing, the report said, adding the explosion happened at a depth of 252 meters (830 feet) and had destroyed ventilation facilities.

Rescuers were focusing efforts on restoring ventilation, the report said.

"The high gas density makes it almost impossible to survive there," Lang Yaoyun, director of the provincial coal mine safety bureau, said.

"It will take some time to bring the density within a safe limit."

Three of the injured were in critical condition and five others were severely hurt, the report said.

China's coal mines are among the most dangerous in the world, with safety standards often ignored in the quest for profits and the drive to meet demand for coal -- source of about 70 percent of the country's energy.

Nearly 3,800 people died in Chinese coal mines last year, according to official figures, although independent monitors say the real figure was likely far higher as many accidents are covered up.