A fallen piece of concrete has forced the closure of the eastbound lanes of Montreal's Ville-Marie Expressway and a partial closure of the westbound lanes.
Police say the 15-metre block of concrete in the Ville-Marie tunnel fell near the City Hall exit. No one was injured and no one was stuck in the tunnel.
"Our officers arrived at the scene and we verified and made sure that no one was stuck underneath the rubble," Daniel Thibaudeau, spokesman for Quebec provincial police, told reporters Sunday.
The part that fell is a screen-like slab meant to block the light, so drivers entering and exiting the tunnel are not blinded.
Construction workers on the scene told the CBC's Peter Akman they had been doing work on the walls of the tunnel and believed vibrations from that may have caused the slab to fall.
Transport Quebec spokesperson Caroline Larose said engineers from the ministry are inspecting the structure. She tried to reassure Montreal drivers, saying the provincial government regularly inspects the city's transportation infrastructure and has invested $4 billion this year alone.
"We won't open this piece of infrastructure until we know it's safe," Larose told reporters gathered near the expressway.
The Ville-Marie is a busy expressway that runs through downtown Montreal. About 100,000 cars travel on it each weekday.
The tunnel was built in 1972, and Concordia University professor emeritus Bala Ashtakala said it is time to replace it.
"I'm really disappointed that they are not taking a good look at the whole situation and doing something about it," he said. "They are doing bits of work here and there — that is not going to solve the problem."
Ashtakala said the lifespan of concrete is 40 years — about the same age as the tunnel.
Previous alarm bells have been sounded over the state of Montreal's aging roadway infrastructure. In 2006, an overpass over Highway 19 in Laval cracked and plunged to the ground below, crushing five people, including a pregnant woman.
The head of a provincial public inquiry into the Laval overpass collapse warned the government that other road structures in Quebec are deteriorating.
It is not known how long the eastbound lanes of the expressway will remain closed, but police and provincial officials are asking drivers to choose another route for Monday morning's commute.