At least 23 miners were missing after torrential rains triggered a cave-in at a colliery in northeast China, state media reported Thursday.

The accident occurred late Wednesday night in a mine in Jixi city in Heilongjiang province, Xinhua news agency said.

Several hundred rescuers worked through the day Thursday to dig out the 23 missing miners without success, it added.

China's coal mines are notoriously dangerous. Official figures show that more than 3,200 workers died in collieries last year, but independent observers say the actual figure could be much higher, as many accidents are covered up.