A crash on the Mercier Bridge forced the closure of the span for the morning rush hour Thursday, causing traffic chaos across the South Shore.

Around 5 a.m. Thursday a snow clearing truck tried to cross the bridge with its trailer in the raised and upright position.

The trailer smashed into the superstructure, driving at least a metre into a space between the steel girders above the bridge deck.

Emergency crews immediately closed the bridge, first in the Montreal-bound direction, and then in both directions as they started figuring out how to remove the wreckage from the span.

The tractor portion of the truck was still functional, and the driver, who is in his 70s, removed it from the bridge with police permission.

"The driver of the truck is not injured, and he's actually with police officers to try and understand what's happened exactly," said Sgt. Claude Denis on Thursday morning.

The Bridge Corporation that oversees the Mercier Bridge said it couldn't allow traffic to cross the bridge until after it has had the chance to determine if there is any damage to the structure.

At 7:30 a.m. the southbound lanes of the bridge were opened to commuters, but the Montreal-bound lanes remained closed. 

The bin was chopped out of the bridge's superstructure at 9:15 a.m., and inspectors began their examination.

Inspectors spent two hours examining the girders before determining there was no significant damage, and it reopened to traffic at 11:30 a.m.

Antoine Vanderzon owns a snow removal company and has been in the business for more than 30 years.

He says in all trucks for the bin to come up, the power take off lever has to be on and another lever pulled.

“Bumps in the road or vibrations, this handle moves even just slightly, a little bit of oil gets into the pump that creates pressure that makes the dumper go up and [the driver] may not notice,” he said.

Vanderzon says in his truck there is a light that indicates the bin is up, but it’s hard to see during the day when the sun is shining.

Police say it's too soon to say if charges will be laid against the driver.