A train carrying petroleum products derailed over Calgary's Bow River Thursday morning after a rail bridge failed. The five-car train derailed on the Bonneybrook Bridge outside a Canadian Pacific rail yard.

Throughout Thursday morning, the bridge continued to buckle as fire and emergency management officials scrambled to learn precisely how dangerous the train’s cargo might be.

Canada's Transportation Safety Board officials were on the scene, and the agency said four of the train carts carried petroleum products and one carries residue of ethylene glycol, a highly toxic chemical component used in antifreeze.

Calgary Emergency Management Director Bruce Burrell said it is possible that the train cars are carrying diesel fuel, but that he could not confirm that.

“Each car could have about 80,000 pounds of product . . . and they’re all flammable liquids,” Deputy Fire Chief Ken Uzeloc told Canada’s National Post. “So if something does go wrong we could have a big pile of burning material.”

The bridge failure is just the latest challenge for emergency crews in the Calgary area, many of whom have been working virtually nonstop since two major rivers — the Bow and the Elbow — burst their banks in Calgary when torrential rain pounded southern Alberta last week.

Police have not said whether the flooding was responsible for the bridge’s structural failure. The city of Calgary has not inspected the bridge because it falls under federal jurisdiction.

Canadian Pacific spokesman Ed Greenberg said the bridge had been inspected Saturday, and the track was inspected Monday.

In Calgary, the city’s Deerfoot trail, a major traffic artery near the derailment, was closed for the morning commute. The city asked motorists — faced with delays of up to three hours — to stay off the roads.