Hammersmith Bridge has been shut to southbound traffic for the rest of the week as transport bosses race to complete emergency repairs.
The discovery of a loose bolt has forced Transport for London to request a week-long closure, which Hammersmith and Fulham Council says will cause "significant delays" as traffic is rerouted via Chiswick.
Bus routes 33, 72, 209, 283, 419 and 485 have been diverted around the bridge until the work is complete, which is expected to be on Friday. Temporary traffic lights had been allowing cars through slowly but TfL this afternoon requested the bridge be shut altogether in one direction.
"The bridge had to be closed unexpectedly on late Friday afternoon after it was found the vibrations from the incessant vehicle traffic had shaken loose a hanger fixing nut," a council spokesman said.
Hammersmith and Fulham Cllr Wesley Harcourt added: "The traffic closure is a safety precaution while we perform an emergency investigation to see if there is any damage to the bridge.
"We need to put the safety of everyone first on what is a very old bridge that was not built to withstand the huge volumes of traffic we have today."
Major refurbishment work is set to close the bridge next summer while it is resurfaced, repainted, strengthened and rewired.
The Grade II* listed bridge was built in 1887.
