One lane on Montreal's Ile-aux-Tourtes Bridge will be closed "indefinitely" after crews found a new crack on the aging structure, the Ministry of Transportation said.

In a news release issued Friday evening, the ministry says the two-lane in each direction configuration that will be in place over the weekend will continue into Monday.

It also warned that it cannot rule out further lane closures as more testing is being done on the bridge that links the western end of Montreal to Ontario.

"As part of its regular monitoring of the condition of the infrastructure, the Ministry paid particular attention to the first frost episodes, and spotted a new crack on the Montreal-bound side of the bridge," the release said.

"The Ministry is already taking steps to reinforce the infrastructure and keep it safe until the new bridge opens, including concrete work this weekend. The extension of the closure by an additional lane is necessary while analyses are carried out on the appearance of this crack. These will determine whether further work is required."

The transport ministry said traffic is safe on the bridge but if anything changes, it could be completely closed to motorists.

The bridge, built in 1965, is reaching the end of its life but is being maintained while a new one started to be built earlier this year. The cost of the project to build the new structure is $2.3-billion and, once it's completed, it will feature three lanes for traffic each way, a bike lane, and shoulders for public transit.