HOHHOT -?Thirty-one miners remained trapped after a coal mine was flooded in north China's Inner Mongolia autonomous region Monday morning, authorities said.

An initial investigation showed 77 miners were working in a pit when the flooding occurred, of which 46 had been lifted to the ground, according to the rescue operation headquarters.

Rescuers were still searching for the 31 missing miners while also trying to drill into the tunnel and pump water out.

Luotuoshan Coal Mine is owned by Wuhai Energy Co Ltd and its parent company is Shenhua Group Corp Ltd, one of China's mining giants.

The mine is still under construction, with the project having started in 2006. It is designed to produce 1.5 million tonnes of coal a year.