Transport Quebec closed a portion of Highway 20 west on Wednesday in the Saint-Simon region of the Monteregie after a failed overpass inspection.
A structural inspection on Tuesday night revealed a potential load capacity problem on the overpass at Rang Saint-Edouard near St-Hyacinthe.
The structure will be closed to traffic indefinitely.
The decision to completely close the section of the highway at the 145 exit was made partly due to an earlier Sept. 21 inspection report.
Detour routes have been set up for both cars and trucks.
Cars can drive the extra two kilometers and take the Rang Saint-Georges exit.
Large trucks must take exit 138 to catch the 224.
It is a similar problem that forced the closure of the Des Chenaux road overpass over Highway 40 in Vaudreuil-Dorion in September.
In that case, MTQ officials said they would decide by the end of October whether that structure could be reopened to the public.
Transport Quebec officials say they are working on a plan to reopen the highway as soon as possible.