Rescuers are combing a south China river and the wreckage of a bridge that collapsed after being hit by a boat in a search for any vehicles or people who were on the structure at the time.

The bridge in Foshan, Guangdong Province, collapsed after being hit by a boat laden with sand at about 5:10 a.m. on Friday, sources with the Foshan traffic police said Friday.

The boat was sailing under the bridge, which connects Jiujiang Township in Nanhai district of Foshan to neighboring Heshan City, when it hit a pier, and at least 150 meters of the bridge structure collapsed.

The collapsed bridge sections fell onto the fore part of the boat, partially submerging it.

All ten crew members were saved shortly after the boat subsided, and two injured crewmen have left hospital after having their bruises treated, an official with the local police said. All crewmen are under police surveillance now.

"So far we don't know whether any vehicles fell into the river, but as the accident occurred at an early hour, there should not have been too much traffic," he said.

He said the boat should not have hit the bridge if it followed navigation markers. The area had seen heavy rainfall in recent days and the higher, faster water may have contributed to the accident.

"I heard a loud noise and then I saw the cement structure of the bridge plunge into the river. It was kind of foggy and I don't know if any vehicles fell into the water," said a local worker surnamed Liu.

"I heard three loud bangs and the lights on the bridge suddenly went out. It was like the bridge had been cut open by a giant knife," said another witness surnamed Yan.

Video footage from a nearby toll station shows about 130 vehicles crossing the bridge between 4:30 a.m. and 5:30 a.m..

Local traffic police are studying the footage and tracking down information on the vehicles to see if any of them is missing. The bridge has been sealed off and traffic is being diverted to a nearby highway. Other boats have been banned from navigating under the bridge.

Traffic police reminded boat owners to be cautious and closely follow navigation rules during flood season.

The local maritime authority dispatched frogmen and ten boats to help with the search.

Li Shenglin, China's Communications Minister, said the ministry has dispatched an investigation team to Foshan, and required local authorities to promptly investigate the cause of the accident.

The bridge, which is about 1,600 meters long and part of Highway 325, was built in 1988 and runs over the Xijiang River, a major tributary of the Pearl River, sources with the Naihai district government said.