The Hongqi Bridge, part of the G317 national highway in Maerkang, Sichuan, gave way around 3 p.m. local time, sending concrete and steel into the river below, according to China Central Television (CCTV).
An official from Barkam County confirmed the incident to the state-run Global Times, saying no injuries had been reported.
Authorities had detected cracks on the bridge’s road surface and right-bank slope a day earlier and imposed temporary traffic controls, according to the report.
Footage circulating on Chinese social media showed the bridge bending before collapsing, releasing a cloud of dust over the gorge.
Local transportation and public security bureaus said the slope showed signs of deformation Monday afternoon, hours before the collapse.
Officials closed the bridge to all traffic and issued safety warnings shortly before it fell.
The structure, completed earlier this year, was a cantilevered two-lane beam bridge spanning 758 meters and standing 625 meters above the valley floor, with piers reaching 172 meters high.
Built by the state-backed Sichuan Road & Bridge Group, the project aimed to improve transport links to the Tibetan Plateau as part of a wider government effort to boost development across western China.
The bridge was intended to symbolize China’s infrastructure progress but had been in service only a few months before the collapse.
Authorities have not yet determined the cause.
Early assessments suggest geological instability may have contributed, officials said.
No vehicles or pedestrians were on the bridge at the time, and investigations are underway.