Rescuers work at the site of a flooding accident of Wangjialing Coal Mine, sitting astride Xiangning county of Linfen city and Hejin city of Yuncheng city, in north China's Shanxi Province, on March 29, 2010.[Xinhua]

Almost 1,000 rescuers were racing the clock through the drizzle Monday to pump water and reach the 153 people trapped underground in a flooded coal mine in north China's Shanxi Province.

Altogether 261 workers were in the pit of Wangjialing Coal Mine, which was under construction, when underground water gushed in at about 1:40 p.m. Sunday. Although 108 were lifted safely to the ground, 153 others were trapped in the shaft.

"Currently, more than 970 people are participating in the rescue operation," said Liu Dezheng, a spokesman of the rescue headquarters and deputy director of the General Office with the Shanxi Provincial Work Safety Committee, at a news conference late Monday.

"If everything goes smoothly, with the installation of two more high-power pumps, it is expected that 650 cubic meters of water can be pumped out of the shaft per hour tonight, and 2,000 cubic meters per hour tomorrow," he said.

Previously, six pumps had been used to pump up to 300 cubic meters of water per hour around the clock.

But Liu also pointed out that complicated conditions underground could hamper the operation.

"The coal mine has a high concentration of gas. Rescuers have to face the danger of toxic gas, while fighting the water," he said. "We must guard against secondary disasters."

Therefore, rescuers had started to drill a hole and open a drainage channel in the shaft to divert water from the flooded tunnel to another unaffected tunnel, he said.

"The channel, with a length of more than 100 meters, is expected to be completed by 6 p.m. Tuesday," he added.

Local authorities have dispatched more than 40 medical workers and 20 ambulances to stand by at the shaft entrance.

President Hu Jintao and Premier Wen Jiabao have ordered local authorities to spare no effort in the rescue operation. Vice Premier Zhang Dejiang is at the site to oversee the operation.

Most of those trapped were migrant workers from Shanxi, Hebei, Hunan and Guizhou provinces, rescuers said.

Xu Shuwei was among the last group of workers to board a lift to escape the flood Sunday afternoon.

"Those trapped are my workmates, I just want to try my best to save them," said Xu, 40, who helped rescuers carry equipment throughout the night.

The mine, which straddles Xiangning County, of Linfen City, and Hejin City, of Yuncheng City, covers about 180 square kilometers.

The mining zone was estimated to have more than 2.3 billion tonnes of coal reserves, including 1.04 billion tonnes of proven reserves, according to the company's official website.

The mine, affiliated with the state-owned Huajin Coking Coal Co. Ltd., is a major project approved by the provincial government. It is expected to produce 6 million tonnes of coal annually once in operation.

Earlier this month, 32 workers were killed in a similar accident when underground water flooded a mine being built in north China's Inner Mongolia Autonomous Region.

One worker died after being lifted to the ground and 31 others were presumed dead two weeks after the accident happened on March 1.

Rescue work, which took 14 days and involved 20,384 people, was halted on March 14 when those trapped were believed to have no chance of survival.