Humen Bridge, which runs across the mouth of the Pearl River in Guangdong province, remained closed on Wednesday, as investigators evaluated its safety after unusual vibrations were reported on Tuesday.
The bridge was closed after a vibration was first reported at about 2 pm on Tuesday. More vibrations were reported on Tuesday night, according to a statement from the provincial Department of Transportation.
The water channel under the bridge was also closed as a precautionary measure.
The department brought 12 bridge experts together to investigate immediately after the vibrations were reported. They said the vibrations were likely caused by wind vortexes.
"The main structure remained intact after the vibrations, so drivers should not be worried about passing over the bridge in the weeks to come," the Transportation Department said.
Even so, drivers who had planned to cross the Humen Bridge were urged on Wednesday to make a detour, the statement said.
The six-lane bridge, which spans 4.6 kilometers, was completed in June 1997 and is a major artery connecting the cities of Shenzhen, Dongguan and Huizhou in the eastern Pearl River Delta with Guangzhou's Nansha district, Foshan, Zhuhai, Jiangmen, Zhaoqing and Zhongshan cities on the west.
The bridge was designed for vehicle speeds of 120 kilometers per hour and can accommodate 80,000 vehicles daily, though it has had major traffic jams during rush hours.