The death toll from a subway tunnel collapse in eastern China rose to seven on Monday, with authorities warning 14 other people trapped underground were likely dead, state press said.

Rescuers found the bodies of four more victims late Sunday and Monday following intense searching in the wreckage of the tunnel that was under construction in Hangzhou city, state radio reported.

Most of the missing were believed to be construction workers whose bodies were likely buried underneath mounds of mud, the report said.

Altogether 75 metres (250 feet) of the tunnel collapsed on Saturday, creating a huge crater that trapped 11 vehicles, including at least one bus, and which flooded with water from a nearby river, it said.

Most of the water was pumped out of the crater on Monday, reports said.

"There is (only) a slim chance of the survival of the trapped workers because of heavy flooding in the crater," Xinhua news agency quoted Wang Guangrong, a spokesman for the local government, as saying.

Rescue workers on Sunday pulled out all the vehicles and brought drivers and passengers to safety, according to Xinhua.

It said that 26 people injured in the mishap had been taken to hospital, with 11 of them released by Sunday.

Hangzhou started construction of a major subway network in March last year.

State press described the accident as one of the worst in the history of subway construction in China.