TAIYUAN - Six men remain trapped underground one day after an illegal coal mine in North China's Shanxi province flooded, the local government said Wednesday.

Liu Xianyun, a production safety official in the city of Yangquan, said water levels in the mine had dropped by just over three meters as of Wednesday morning, as rescuers have been working to pump water out of the mine.

More than 3,100 cubic meters of water have been pumped out of the coal mine and 375 cubic meters of water are being pumped out every hour, Liu said.

Local rescuers said their work has been difficult because of a lack of geological data.

"Water levels underground remain greater than two meters. Judging from the amount that has been pumped out and the current water level, water has been continuing to flow into the mine," Liu said.

Liu said rescuers will install more water pumps to speed up the process, as they cannot enter the mine to find the stranded miners until the floodwaters are completely drained.

Medical workers are standing by in order to give survivors timely emergency treatment.

The accident happened at about 4 am Tuesday in Yangquan, where twelve people illegally dug a mine pit in a residential building. Six of the 12 managed to escape the flood.

A local resident claimed that farm vehicles had been used to transport coal from the residence Sunday evening.

The government of Yangquan has initiated a campaign to discourage illegal mining. The government is investigating related cases and encouraging local residents to report illegal mining operations.