Portage Avenue has reopened in both directions as officials assess the damage from a bizarre fire this afternoon in a culvert for Truro Creek.
Traffic is reduced at Sackville and Lyle streets along Portage.
The blaze began shortly before 2 p.m., near the intersection of Portage Avnue and Albany Street.
"We had heavy flames and black smoke emitting from the north end of the culvert, and within about 10 minutes it started to come out the south end as well so we had a fairly heavy toxic cloud coming out of that and travelling northeast," said Ian Campbell with Winnipeg Fire Paramedic Service.
"What caused our problem was the plastic or polystyrene liner on the inside of the culvert. Once that got going it created the smoke and heavy flames."
The fire sent a large, dark cloud of smoke into the sky over St. James before firefighters got it under control.
Portage Avenue is blocked in both directions between Lyle Street and Ferry Road while officials wait for structural engineers to assess possible damage underneath the road due to the heat from the blaze, Campbell said.
Environmental officials are also checking the quality of water downstream on Truro Creek, he said.
The cause of the fire is not yet known. The arson strike force is investigating and asks anyone with information to contact investigators at (204) 986-6813 or CrimeStoppers at (204) 786-TIPS (8477).