A coal mine explosion in southeastern China has killed 13 miners believed to have been intoxicated by poisonous gas, the official Xinhua news agency reported on Thursday.

Local officials had said 36 miners were underground when the blast occurred on Wednesday at the Xinglong Mine in Sichuan Province, but that more than 20 were rescued, Xinhua said in an earlier report.

"We rushed to the scene and set up rescue teams. In the afternoon, about 30 rescuers went down the shaft," Xinhua later quoted Xiao Ronghua, Party Chief of Luxian County, as saying.

An investigation of the cause of the blast was still under way, it said.

The Xinglong mine, with annual output of 60,000 tonnes, was operating legally.

China, which has the world's deadliest mining industry, has been struggling to clean up the sector, which last year killed more than 4,700 people.

Owners continue to push production beyond safe limits to reap profits and meet the country's surging appetite for fuel.