A road bridge under construction across a river in southern China collapsed, killing 22 people and injuring 22, state media reported on Tuesday, but witnesses expected the death toll to rise substantially.

At least 39 people were missing after the 320-metre (1,000-foot) concrete arc bridge spanning the Tuo river in Fenghuang county, Hunan province, collapsed on Monday during the evening rush hour, Xinhua news agency said.

Some 400 police had been sent to the scene to keep order, Xinhua said.

Pictures showed bulldozers and rescue workers picking through a massive pile of debris stretching between two hills at the banks of the river.

"I saw a lot of bodies lying on the road, some of them were construction workers, and some were passers-by ... blood was everywhere," Yang Shunzhong, a witness, told Reuters.

"A car was crushed flat under the bridge, it was so ruined that I could not even tell the size of the car," he said by telephone.

Police told Yang that they had found about 60 bodies, and more rescue workers were searching for the missing buried amid the ruins and in the river below.

State-run China Central Television reported the death toll at 22, but Yang said "people on the scene" told him it could rise much higher.

"A lot of women and children were on the scene, crying and looking for their families or friends," Yang added.

DANGEROUS BRIDGES

A total of 123 workers were at the site of the 42-metre (138-foot) high bridge, which had been scheduled for completion this month, Xinhua said.

They had been "dismantling steel scaffolding erected during the construction process" at the 12 million yuan ($1.58 million) bridge since mid-July, it added.

Part of the bridge collapsed across a highway linking Fenghuang county to an airport in neighbouring Guizhou province's Tongren region, according to a notice posted on the local government Web site on Tuesday.

The accident was under investigation and police had detained a construction manager and a "project supervisor" for questioning, the agency said.

Hunan's provincial governor, Zhou Qiang, and vice-governor Xu Xianping were on their way to the site, it added.

The bridge's collapse came as state media reported that China would fix more than 6,000 damaged or dangerous bridges across the country. A bridge collapse in June in the southern province of Guangdong killed nine people.

An editorial in the China Daily warned that thousands of the country's bridges had been categorised as "unsafe".

"If left unrepaired these bridges may crumble at any time, wreaking economic havoc and possibly claiming human lives."

The bridge disaster occurred days after the death toll from the Interstate 35W bridge's Aug. 1 collapse into the Mississippi River in Minneapolis was raised to nine.