Quebec Transport Minister Francois Bonnardel said Thursday on Twitter engineers decided to close the Ile-aux-Tourtes bridge for the safety of its users.
A Transport Department news release said workers observed damage to reinforcing rods that could have weakened the structure of the aging bridge.
Shortly after 5 p.m., traffic cameras showed access to the bridge closed off, and the Transport Department said the closure is expected to have significant repercussions on traffic.
The Ile-aux-Tourtes bridge links the western tip of the Island of Montreal with the town of Vaudreuil-Dorion, Que., and is used by 87,000 vehicles a day, 10 per cent of which are trucks.
The bridge was put into service in 1965, and the Quebec government says it is in the planning stages of rebuilding the structure.