The southbound lane of the Louis-Hippolyte-Lafontaine Tunnel closed Wednesday night and will not reopen until Saturday as crews remove concrete grids.
Transport Quebec officials decided to take a closer look at the tunnel after 25 tonnes of concrete came crashing down in Montreal's Viger Tunnel in July.
Transport Quebec found that the beams holding the concrete grids in the Louis-Hippolyte-Lafontaine Tunnel were starting to show damage.
The grid panels are designed to dim the outside light so drivers can adjust their eyes as they go in and out of the tunnel.
But according to Caroline Larose of Transport Quebec, the removal of the grids won't mean drivers will be blinded when they use the tunnel.
"Of course there is a safety issue, but all the lighting system was remodeled in 1996 so we have a good lighting system in there," she said.
Larose said the speed limit will be reduced to 50 km per hour to help reduce the risk of accidents.
The northbound side of the tunnel will remain open during the day, but it will be reduced to one lane at night.
Transport Quebec said there will likely be more closures in the tunnel in coming weeks as they work to remove the concrete grids.