The number of people trapped underground after a coal mine flooding in north China's Shanxi Province was revised - for a second time - to 153 from 123, rescuers said late Sunday night.

A photo taken on March 29, 2010 shows a rescuer at work after the flooding in the pit of Wangjialing Coal Mine, which sits astride Xiangning county of Linfen and Hejin of Yuncheng in north China's Shanxi province. The number of people trapped underground after the accident rose to 153, rescuers said late Sunday night. [Photo/Xinhua]

Investigations showed that 261 workers were in the pit of Wangjialing Coal Mine under construction when underground water gushed in at about 1:40 pm. Of them, 108 were lifted safely to the ground while 153 others trapped in the shaft, according to the rescue headquarters.

"Most of the trapped are migrant workers from Shanxi, Hebei, Hunan and Guizhou provinces," a rescuer said.

The exact number of people trapped is still being checked.

Soon after the accident happened, the Shanxi Provincial Work Safety Administration and the Shanxi Provincial Emergency Affairs Office said 152 people were trapped underground, but officials later changed the figure to 123.

Rescuers are struggling to save the trapped people, and local authorities are investigating the cause of the accident.

President Hu Jintao and Premier Wen Jiabao ordered local authorities to spare no effort to save the trapped while guarding against secondary accidents.

Vice Premier Zhang Dejiang rushed to the site late Sunday to oversee the search and rescue operation.

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

The mining zone boasts more than 2.3 billion tonnes of coal reserves, including nearly 1.04 billion tonnes of proved reserves, according to the company's official website.

It is now under infrastructure construction and is expected to produce 6 million tonnes of coal annually once put into operation.

The mine, affiliated to the state-owned Huajin Coking Coal Co. Ltd., is a major project approved by the provincial government.