At least 33 people have been trapped in a coal mine in central China, state media has reported.
The miners became stuck underground after an explosion on Monday night at a mine in Baofeng county, Henan province.
According to Xinhua news agency, another explosion shook the mine as a rescue attempt got underway, hampering efforts to save those trapped.
China's mines are among the most dangerous in the world, with about 5,000 deaths reported every year.
Independent labour groups put the death toll at much higher - up to 20,000 annually.
They say there is evidence that mine operators often cover up accidents to avoid costly shutdowns and fines.
Last year Beijing pledged to close all small coal mines, in a bid to improve the industry's safety record.
But coal provides more than two-thirds of China's electricity, and production has been stepped up to meet demand.