A bridge that collapsed in China killing at least 36 people broke apart like a pat of beancurd because there were apparently no steel reinforcement bars, state media said on Wednesday, quoting a rescuer.

More than 1,500 people were searching for about 30 missing people following Monday's disaster on the 320-metre-long (1,050-foot) bridge on the verge of completion across the Tuo river in the southern province of Hunan, the Beijing News said.

But they held out little hope of finding survivors and health authorities were spraying disinfectant into the water to prevent the spread of disease from bodies spreading down river.

Because the bridge and pillars have all collapsed, it will be very difficult for rescuers to find or save people buried in the debris, deputy rescue director Luo Ming was quoted as saying, adding they had to blast open the concrete to retrieve bodies.

Twenty-two injured, mostly workers building the bridge, were in a state of shock, the newspaper said.

They are generally very scared. Some are unconscious, and others who can talk are very tense, a doctor was quoted as saying.

Most parts of scenic Fenghuang county have had their water supplies cut off since the accident as the collapse of the bridge damaged water pipelines, it added.

Police have detained a construction manager and a project supervisor for questioning. Premier Wen Jiabao urged the local government to deal with the issue seriously, the newspaper said.

The work safety and quality watchdogs were investigating the cause of the collapse, but the newspaper quoted a rescue worker as saying that the bridge was mainly built of stone and concrete.

No reinforced steel bars were seen in the collapsed bridge supports. It was like a knife cutting through tofu (beancurd), Hou Jiaping, a rescue worker, was quoted as saying.

Pictures in newspapers supported his comments. Sections of the bridge lay flat on the ground, lumps of rock bursting through the concrete and no steel bars to be seen.

The official China Daily called the accident a bloody lesson and said human factors might loom large behind the sorry scene.

(It) should also prompt a sweeping check of the safety procedures in place at all current bridge construction projects, it added.

Workplace accidents are rife in booming China, where patchy safety enforcement and corner-cutting by contractors result in the deaths of thousands in the country's coal mines, factories, building sites and on public works projects every year.

The newspaper on Tuesday had warned that thousands of the country's bridges were unsafe. If left unrepaired, these bridges may crumble at any time, wreaking economic havoc and possibly claiming human lives, it said.