At least 30 miners were feared trapped after an accident on Saturday at a coal mine in northeast China, state media reported.
Some 44 miners were working underground at the mine in Hegang, Heilongjiang province, when the accident occurred at around 4:00 am, Xinhua news agency said, quoting local authorities.
Around a dozen miners escaped but more than 30 could be trapped in the mine, it said.
It was not immediately known what caused the accident.
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 surging demand for coal the 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 is probably much higher since many accidents are covered up.