The was still a chance of survival for 10 trapped in a collapsed railway tunnel in southwest China's Guangxi for four days, although two new cave-ins had disrupted their contact with rescuers for more than 24 hours, said rescuers Thursday.

"Our equipment has detected signs of life under the debris, and the trapped workers have air and enough water and food, which had been passed through the ventilation holes before the secondary cave-ins occurred Wednesday," said Lu Chunfang, vice minister of railways, who is overseeing the rescue work at the site.

He said rescuers hoped to dig a passage to reach the trapped by Friday afternoon.

The cave-ins on Wednesday morning blocked two of the four ventilation holes drilled by rescuers to where the 10 workers have remained trapped after the tunnel, under construction, collapsed at around 4 p.m. Sunday.

Lu said rescuers are pumping fresh air through the two remaining ventilation holes, and air flow motion had been detected indicating that the living space remained intact after the secondary disasters.

Before the new cave-ins, the workers -- huddled together in a small living space -- were reported to be in good condition and they had been communicating with rescuers with paper notes passed through the ventilation holes.

Rescuers had been able to pass water, milk, canned porridge, flashlights, paper and pens to the trapped workers. The hungry workers had asked for bread, but rescuers persuaded them that they were too weak to eat food other than milk and porridge.

The tunnel was being built by the No. 18 Bureau of the China Railway Group Ltd. Workers had dug 300 meters of the 800-meter tunnel when the accident happened Sunday.

The line that will use the tunnel will connect Nanning and Litang, an industrial town in Guangxi.