A bridge under construction collapsed in Fushun city, Northeast China's Liaoning province, June 18, 2012. The 416.4-meter bridge over a river cost 29 million yuan ($4.6 million) in local government investment and was expected to be completed by July 1, 2012. The cause of the collapse is still unknown and no injury was reported. [Photo/CFP]

SHENYANG - A bridge in the city of Fushun, Northeast China's Liaoning province, collapsed Monday evening, just one month before the bridge's scheduled opening to traffic.

A witness said that the collapse happened after a rainfall that occurred at about 5 pm.

Initial investigation showed that the collapse was caused by workers' irregular operation, according to local government sources.

Several workers dismantled supporting facilities before reinforcing of a part of the bridge was completed, said the sources.

Construction on the bridge began in November 2011. The bridge was scheduled to be completed on July 30, according to a government plan.