Rescuers are working to free seven miners trapped underground for more than 24 hours after a flood in a coal mine in north China's Shanxi Province early yesterday.

The flooding started in a ventilation shaft in the Qinghai Coal Mining Co., Ltd, Xiangning County, at 6:30 am, trapping seven of the 11 miners working the night shift, said police.

A total of 83 rescuers from the ambulance corps and four nearby mines were working at the scene, said a Shanxi Work Safety Administration spokesman.

One pump was expelling 63 cubic meters of water from the shaft every hour, and four other pumps were being set up and were expected to begin operating soon, the spokesman said.

Police and work safety officials are investigating the cause of the incident and questioning mine officials. A police spokesman said they had frozen the mine owner's bank account, which was standard procedure in such investigations.

The licensed private mine has a production capacity of 300,000 tons.