An underground fire at an illegal coal mine in northeast China has left 11 people dead, with one still missing, state media reported Friday.

The blaze broke out at a mine in Liaoning Province early Monday, trapping 13 miners about 500 metres (1,600 feet) underground, the official Xinhua news agency said.

Two bodies were found Thursday and nine more Friday. Rescuers have recovered one miner alive but Xinhua cited a local work safety bureau as saying one person remained missing.

Despite being closed in 2004, the mine was able to continue operations after the owner concealed the shaft within a coal washing plant, Xinhua said, citing head of the bureau Hao Chijun.

Hao said the illegal mine only had one opening, whereas normal mine shafts have at least two, Xinhua reported.

China is the world's largest coal producer, and deadly accidents in the sector are common.

The government says fatalities are declining, but some rights groups argue that under-reporting means the actual figures are significantly higher.

At least 19 people in China were killed in a coal mine accident in March, in what is believed to be one of the deadliest such incidents this year.