Beijing - A small cave-in and surface cracks preceded the collapse of a road into a subway tunnel in eastern China, but did not lead to the suspension of construction work, state media said on Monday.

Rescue workers were still removing the steel frame from the tunnel so that they would be able to dig for 14 people still missing since the collapse on Saturday in the city of Hangzhou, China Central Television said.

The bodies of seven victims had been recovered and rescue officials held little hope of finding anyone alive in the 15-metre-deep crater, which flooded immediately after the tunnel collapsed.

The broadcaster quoted a safety official as the tunnel construction should have stopped after the small cave-in and the cracks in the road were noticed on unspecified dates.

But a second official was quoted as saying that construction managers had been waiting for approval from a higher level to suspend work.

The collapse trapped dozens of construction workers and caused 11 vehicles to fall into the hole, which was about 75 metres long and 50 metres wide.

It also damaged three apartment buildings, one of which was demolished on Monday, and forced the closure of a nearby school.

The official China Daily newspaper on Monday ran a commentary on the accident called "Learning the lesson."

"It is still too early to conclude that it was caused by human errors either in construction or design," the commentary said of the collapse.

"But it is undoubtedly important for the investigation to find out the exact cause behind it, not only for the continuation of this project, but for other upcoming infrastructure constructions," it said.

The newspaper ran a separate story quoting Shen Jingyan, a chief engineer for the Ministry of Construction, as saying subway projects needed "very careful geological research and a detailed all-round risk evaluation before work starts."

"Authorities must improve management, and quality should not be compromised in trying to complete the projects in record time," Shen said.

Some 2,000 rescue workers pumped water up to 6 metres deep out of the hole left by the collapse in Hangzhou, and divers searched the site for survivors on Saturday and Sunday.

Local hospitals treated at least 19 rescued people, including two in serious condition, while witnesses and rescuers earlier said at least 50 people were trapped.

About 30 construction workers and 27 bus passengers managed to escape after the collapse, reports said. (dpa)