MONTREAL - This could be another tough day for commuters in Montreal.

This, after a 15-metre-long concrete slab dropped Sunday from the ceiling of a tunnel along the downtown Ville-Marie expressway.

That prompted transport officials to knock down another unstable beam in the same tunnel yesterday.

Amid public pressure yesterday, the Quebec government released a pair of alarming inspection reports conducted on the tunnel in 2008 and 2010.

The 2008 study warned that the tunnel was in a "critical" general state concerning user safety and it recommended safety work to be done.

It also warned that parts of a duct bank could collapse onto passing cars.

Montreal's aging road network has forced lane closures on several overpasses and bridges this summer, as engineers scramble to deal with crumbling infrastructure.

The closed routes in Montreal have resulted in traffic-congestion nightmares across the city -- even at the oddest hours.

Structural engineers say Montreal's woes are a warning for other Canadian cities of what could happen when a municipality doesn't have a solid maintenance plan in place -- from the very beginning.