A section of a Japanese-funded bridge under construction in southern Vietnam collapsed on Wednesday, killing up to 60 workers and injuring about 100 in the country's worst such disaster.

A contractor with a Chinese company working on the bridge being built in Can Tho city said 60 people were killed. State-run Vietnam TV reported 55 dead, 97 injured, including 17 with critical head injuries.

TV news bulletins showed footage of a mass of tangled steel and concrete at the scene, and emergency workers in white uniforms taking bloodied victims into hospitals for treatment.

Civilians also contributed by helping to carry the injured on stretchers to hospital and others donated blood, officials said, adding at least 150 people were being treated for injuries.

"I'm in shock. I feel helpless. I couldn't do anything," a blood-splattered survivor, Tran Minh Thu, said in a TV interview.

Officials said the rescue effort would continue around the clock. "They are using machinery to cut and lift the concrete," a police official in Vinh Long said by telephone. "It is very difficult to reach the bodies and there is also danger of further collapse."

The Can Tho director of health said rescuers had not been able to find any more victims since late afternoon.

"Now the focus is on 17 patients in a very critical situation," said the official, Le Hung Dung.

Doctors and nurses were sent from Ho Chi Minh City, 170 km (105 miles) away, to help.

Official media said the collapse of a section of bridge on land next to the Hau River was the worst bridge accident in Vietnam, which is ramping up infrastructure projects to keep pace with an economy growing at more than 8 percent a year.

The cause of the collapse was not immediately known, but Vietnam TV reported that rains may have softened the foundation.

Prime Minister Nguyen Tan Dung, who is attending the United Nations General Assembly in New York, ordered an investigation.

The Japanese embassy in Hanoi said it was still checking whether any of its nationals were among the 250 workers on site at the time of the 8:30 a.m. (0130 GMT) collapse.

The bridge is being built to link Can Tho and Vinh Long province over the heavily used Hau river, one of nine tributaries of the Mekong river.

Japanese companies started building the bridge in 2004 with Japan government aid of $300 million. It was to be finished next year and have a span of 2.75 km (1.7 miles).

Three Japanese contractors -- Taisei Corp, Kajima Corp and Nippon Steel Engineering Co Ltd -- were on site on Wednesday.

Petrovietnam Insurance said it is the insurer of the bridge under a contract worth about $200 million. PVI said it has hired international inspector Crawford & Co to investigate.

The company said that even though PVI provided only insurance for the bridge it would still compensate victims.

(Additional reporting by Nguyen Nhat Lam)