TORONTO -- Concerns about the safety of the Gardiner Expressway grew on Monday as more pieces of concrete fell from the raised highway, striking a vehicle travelling underneath.

Toronto police said concrete pieces fell from the Gardiner near Lakeshore Boulevard and Yonge Street shortly before 11 a.m.

A slab struck the windshield of a Mercedes-Benz in traffic, leaving driver John Pandell shaken but uninjured.

“There was a loud boom; it sounded like a gunshot or an explosion. It really startled me, so I pulled over,” Pandell told CP24.

Pandell’s Mercedes-Benz was struck several times by pieces of concrete, denting the roof and truck.

“I think it is fairly damaged, to be honest with you,” he said.

Two westbound lanes of Lakeshore Boulevard and the ramp onto the westbound Gardiner have been blocked off as police investigate.

The city recently stepped up its safety checks along the raised highway after several incidents of falling concrete. Pieces of concrete fell into traffic in three separate incidents last month.

City engineers say the pieces of concrete come from the road’s façade and that the highway remains safe for travel.

Toronto Mayor Rob Ford estimates repairs on the expressway could cost more than $150 million.

Ford says he would consider asking the provincial and federal governments to help cover the cost.