The blast occurred at the Rui Zhiyuan mine in Shanxi province's Linfen city, state-run news agency Xinhua said. It is not clear what caused it.

Xinhua said 15 miners had either been rescued or escaped themselves.

China's mines are among the most dangerous in the world, with about 5,000 deaths reported every year.

Rescue mission

"After the accident occurred, the mine sent in a rescue team of 32 people, but soon after they were trapped as well," a spokeswoman for the government department on safety at work, An Yuanjie, told the AFP news agency.

She was unable to say what caused the explosion.

Xinhua said rescue workers believed managers at the mine had tried to launch a rescue operation by themselves, "which magnified the number of casualties".

It said they were being questioned by police - and the mine's bank account had been frozen.

Safety at the mine is the responsibility of its owner, the local government.

No surprise

The facts of this latest mine disaster are grimly familiar, says the BBC correspondent in Shanghai, Quentin Somerville.

China - and perhaps the rest of the world - is growing used to this loss of life.

Thursday's accident was reported on the state-controlled lunchtime news, but most viewers will be neither shocked nor surprised, he says.

After all, an average of 13 miners are killed every single day down the pits. In August, 181 miners were killed when floodwater poured into a mine in Shandong province in the east of the country.

Rising demand for energy and fuel means that owners and local officials often ignore safety issues in pursuit of profits.

The government has launched an ongoing safety campaign, and keeps calling for more to be done.

Officials warned recently that as mines increased output to meet increasing winter demand, accidents were even more likely to happen in the next few months.