Beijing, July 21 (IANS): Thousands of rescue workers and local volunteers are searching for people still missing after their vehicles plunged into a flooding river when a highway bridge collapsed in northwest China's Shaanxi Province.

Local authorities have said that the number of professional rescue workers at the site had increased to 1,630 by 2 p.m. Sunday, more than a day after the collapse that has already left 12 dead and another 31 missing.

Aided by 205 vehicles, 63 vessels and 82 drones, they are combing through a 70-kilometre stretch of Jinqian river downstream from the collapse site, Xinhua news agency reported.

More than 1,500 local residents have also joined the search.

A 40-meter section of the No. 2 Bridge in Yanping village came down at about 8.40 p.m. Friday, after a heavy rainstorm triggered a flash flood on Jinqian river.

Rescue personnel have said that river torrents have slowed and water levels have dropped on Sunday, allowing them to locate vehicle wrecks more easily.

On Sunday morning, Xinhua reporters saw a truck being retrieved from the riverbed 500 meters downstream of the collapse site. No driver or passenger was found along with the wreck.