The whereabouts of the 24 miners who had been trapped for two days in a flooded colliery in northeast China's Heilongjiang Province remained unknown Monday, local authorities said.

Rescuers had drilled nearly 100 meters down the pit but were still unable to get in contact with any of the victims, a result of high gas density and rising water levels, said Fang Dongchu, deputy chief of the emergency rescue headquarters at Hengxinyuan Coal Mine in Hengshan District of Jixi City.

The maximum gas density was 6 percent after the flood, making it impossible to pump the flood water, said Fang.

Rescue work could continue only when the gas density was below 1 percent, he said.

"By the time two pumps began working Monday morning, the water level in the main shaft had risen to 140 meters," said Fang. The water level was 87 meters Saturday afternoon.

The accident happened at 1:30 p.m. Saturday, when 26 people were working in the pit. The only escapees were two managers in charge of production.

Two safety officials have been removed from their posts for dereliction of duty, including Qin Xuyuan, a deputy official in charge of work safety in Hengshan District, and Zhang Yidong, director of the district's coal mining bureau.

Hengxinyuan Mine was founded in 1997 with a designed annual output of 60,000 tonnes. The mine was scheduled to be closed before the end of this year.