The Traffic Bridge, shown in this Google Street View image, has been closed indefinitely after worse-than-expected corrosion was found on the steel-truss structure. (Google)

Saskatoon's oldest bridge has deteriorated to the point that it's about to collapse, Mayor Don Atchison says.

The Traffic Bridge, also known as the Victoria Bridge, was closed indefinitely on Tuesday because of safety concerns over corrosion. The concern is that the steel-truss structure over the South Saskatchewan River could collapse under its own weight.

"It's not a question of being able to fix it properly," Atchison told reporters on Wednesday. "The bridge is going to collapse. It's imminent that it is going to collapse. And so the question is, 'How can we best deal with the situation?'"

The 103-year-old structure that connects Victoria Avenue to 3rd Avenue South and Spadina Crescent is a crucial route for commuters heading home from the downtown.

'The bridge is going to collapse. It's imminent that it is going to collapse.'—Saskatoon Mayor Don Atchison

A four-day inspection had been under way, but inspectors found more corrosion than they expected. City officials decided to close the bridge immediately late Tuesday afternoon.

"We're going to continue the inspection for the rest of the week, keep the bridge closed," said Mike Gutek, the city's general manager of infrastructure services.

"We'll be able to evaluate where we're at with the condition and the safety of that structure."

Some motorists CBC News spoke with Wednesday appeared shocked that their favourite bridge was out of commission.

"Indefinitely! Oh my goodness," said Audra Oosthoek who found her usual route blocked. "With all the traffic closures around right now, this is the only way to get there, besides going all the way around."

Saskatoon is already in the midst of public consultations on the future of the Traffic Bridge. One proposal suggests it could be used for pedestrian and bicycle traffic only.

Right now, it can't be used by anybody, Atchison said.

"If it's going to collapse under its own weight, it's no longer safe for pedestrians; nor is it safe for vehicles," he said.