Rescuers on Monday heard sounds made by 10 trapped workers in a collapsed railway tunnel under construction in southwest China's Guangxi Zhuang Autonomous Region.

A 40-50 meter long section of the railway tunnel being built in Binyang County of Nanning, the regional capital, collapsed at about 4 p.m. Sunday, trapping 10 miners, instead of the previously reported 9, said Sun Jun, an official with the rescue headquarters.

"The latest sound of knocking-on was heard at 10:00 a.m. Monday," he said.

Rescuers first heard the sounds made by the workers Sunday midnight, after they dug the first hole for ventilation to the collapsed section. By Monday morning, the second hole had been dug to ensure enough air in the collapsed tunnel, Sun said.

"We have found there might be a space of 8 meters long in the collapsed part. Rescuers are building supporting structures before drilling a passage to get the trapped workers out," he said.

He said that workers had dug 300 meters of the tunnel, which was to be 800 meters long, when the accident happened.

The tunnel construction project has been undertaken by the No. 18 Bureau of the China Railway Group Ltd. for a rail line connecting Nanning and Litang, an industrial town in Guangxi.