The collapse of a large slab of concrete from the ceiling of a Montreal tunnel on Sunday is raising questions about why more hasn't been done to improve Quebec's crumbling infrastructure.

Police said no injuries were reported and no one was trapped inside the Ville-Marie Tunnel when a large lighting support beam fell onto the eastbound lanes near the City Hall exit at about 9:30 a.m. on Sunday. The beam, measuring nearly 15 metres in length, is a screen-like slab meant to block light.

Construction workers were on site at the time, digging nearby in another tunnel. They said there was heavy shaking in the tunnels caused by machinery.

Structural engineer Hellen Christodoulou told CTV Montreal on Sunday that there is either a problem with on-site inspections, or safety precautions were not taken during the construction work.

"We have too many examples at this point that warrant a little more diligence in the type of the work that's being done and the organization," she said. "We have had a sort of a history in the last few years of problems."

In 2006, five people were killed when a 19-metre chunk of concrete fell from the De La Concorde overpass in Laval. In 2000, one person died after concrete fell off Laval's Boul. Du Souvenir overpass while it was under construction.

Christodoulou said after the 2006 incident, there were 135 bridge structures that were scheduled to be replaced or restored. She said the province promised a major review of bridges and overpasses.

"The way the situations have arisen and the type of problems that we have, it warrants big changes," she said.

The cause of the collapse in the Ville-Marie Tunnel, which is located near the Hotel-de-Ville, is still unknown.

The tunnel was closed all day on Sunday as dozens of emergency officials, authorities and engineers studied the structure.

On Monday, transport officials knocked down another unstable beam in the tunnel using a crane.

A spokeswoman for the provincial Transport Department told The Canadian Press that workers are also working to stabilize a third beam.

Officials said the tunnel won't be re-opened until it is declared safe.

The Ville-Marie Tunnel opened in 1974 and serves up to 150,000 cars on weekdays.

With files from CTV Montreal and The Canadian Press