The Victoria Bridge is closed in both directions Tuesday to make way for emergency repairs.
According to the Quebec Transport Ministry (MTQ), urgent work started to fix an aqueduct following a road collapse in Montreal near the bridge at 7 a.m.
Work is expected to last until Wednesday, but the MTQ could not provide a specific reopening time.
Anyone who usually uses the thoroughfare is being asked to reroute to one of the other bridges.
The Victoria Bridge, which opened in 1859, is one of the main links between Montreal and the South Shore.