BEIJING — Thirteen people have been found dead after a gas explosion in a Chinese coal mine, and 20 others are still trapped, their status unknown, state media said Tuesday.

Rescuers worked through the night at the privately owned Jinshangou mine in the Chongqing region where the explosion occurred before noon Monday, Xinhua News Agency reported. Two miners escaped earlier.

Rescuers work Monday at the Jinshangou Coal Mine in Chongqing, southwest China, where a gas explosion killed more than a dozen workers. Hundreds of rescuers were hindered by debris as they worked through the night trying to find another 20 miners. Tang Yi/Xinhua via AP

Xinhua previously reported 15 deaths in the explosion, but said Chongqing’s deputy mayor, Ma Huaping, lowered the death toll in a news briefing early Tuesday, saying only 13 bodies had been found so far. Local officials did not answer telephone calls from The Associated Press, and a person who answered the phone at the mine hung up when asked about the blast.

“We are still working all-out to search for the 20 missing miners, and will exert our utmost as long as there’s still a ray of hope,” Ma said, according to Xinhua.

Xinhua reported that the 400 workers trying to rescue more miners were being hindered by debris blocking some of the mine’s passageways.

Gas explosions inside mines are often caused when a flame or electrical spark ignites gas leaking from the coal seam. Ventilation systems are supposed to prevent gas from becoming trapped.

The State Administration of Work Safety ordered an investigation into the blast, “adding that those responsible must be strictly punished.” Local officials in Chongqing also ordered the temporary shutdown of coal mines producing less than 90,000 tons a year, Xinhua said.

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