Rescuers on Friday heard the sound of knocking on pipes at a flooded north China coal mine where 153 miners have been trapped for five days.

Pan Zengwu, deputy chief of the Shanxi provincial coal geological bureau, said rescuers heard what they believed to be the trapped miners making the noise at 2:15 p.m..

The rescuers knocked on the drill pipe to respond, Pan said.

He said the rescue team sent 300 bags of glucose, each 200 ml, down the 250-meter pit.

Rescuers have been drilling holes to pump out water and send down food.

An iron wire was found attached at the end of a drill pipe when it was lifted to the surface at 3 p.m..

Pan said this was apparently tied on by the trapped miners.

At about 1:40 p.m. Sunday, underground water gushed into the pit of Wangjialing Coal Mine, which was under construction, when 261 miners were working underground. Altogether 108 were lifted safely to the surface.

About 3,000 rescuers are racing the clock to pump water and reach the trapped miners.

The water level underground had dropped by 2.6 meters by Friday noon after a total of 57,900 cubic meters of water had been pumped from the shaft.

Rescuers said the trapped miners were working on nine different platforms, and four platforms had not been totally submerged, making it possible that some workers could have survived.

The mine, which straddles Xiangning County, of Linfen City, and Hejin, a county-level city within 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 to 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.

If the trapped workers cannot be saved, the accident will be the China's worst mining disaster in more than two years. In August 2007, a total of 181 workers died at two flooded coal mines -- 172 at one mine -- in Xintai, eastern Shandong Province.

Meanwhile, the death toll from a gas explosion at a coal mine in central China's Henan Province Wednesday had risen to 19, and about 24 people were believed still trapped underground, local authorities said Friday.