Emergency crews are keeping a close watch at the scene at Speedway International Inc., which manufactures Pro Comp Racing Methanol racing fuel.
The fire is now under control but there is a concern that hot spots could flare up.
The blaze, which ignited at about 5:30 p.m. Monday, forced the evacuation of about 100 nearby homes west of the plant and roared loudly as it shot flames and choking, heavy black smoke high into the sky.
By the time the streets in the area were reopened and most evacuees were allowed to return it was early Tuesday morning and it looked as if a bomb had hit the plant, which was melted from intense heat, said fire platoon chief Ted Kuryluk.
No injuries have been reported to date.
Fire officials reported Tuesday morning the damage is estimated at $15 million. The challenge now is to figure out what caused the massive fire.
"[There's] lots of damaged rail cars and tanker trucks and automobiles," fire chief Bill Clark said Tuesday.
"The building, which is probably 400 or 500 feet long by 100 feet wide … it's completely flattened."
Kuryluk said the blaze is the largest fire Winnipeg has seen for almost 25 years, when another chemical fire erupted in the same St. Boniface industrial park in 1990.
Asked on Tuesday what the scene looks like, Kuryluk said, "Totally devastated."
"It's just a shell of a building; shell of a number of trucks and equipment and some rail cars outside," he said.
The fire produced a thick chemical smell and dropped sooty debris over a large area in St. Boniface.
Some residents near the fire who watched that debris fall into their yards wondered why their homes weren't evacuated.
"What's going on? How come we're left in the dark? How come people on the east side of the fire weren't notified?” said Wayne Mezzo, who lives on Dugald Road, east of the fire.
A hot black foamy substance rained down on his yard and he wants to know what it was made of.
“We want to know what's falling from the sky. Whatever that was in my hand, it had a chemical smell to it and it was still hot," he said.
Emergency officials said the evacuation area they identified on Monday was based on wind conditions at the time and the location of possible fuel sources.
Fire officials also said people should not be worried about smoke and debris from the fire being toxic because the fire's main source was clean-burning fuels.
Employees numbed by blaze
Speedway International employs eight people, all of whom had left the building before the blaze erupted.
One of them, who spoke to CBC reporter Meaghan Ketcheson on Tuesday, said everyone is shocked by what happened.
Barney Osadchuk, who runs a trucking company next to Speedway, said the owner was devastated while watching the fire Monday night.
"He was more heartbroken than anything else and I imagine he was pretty confused, wondering what the heck happened, Osadchuk said.
"He told me he got the call from his security system, you know, that the alarms were going off."
The Manitoba government says it has given more than $800,000 to Speedway International Inc. over the past four years.
Most of that funding — $779,000 — has been in the form of "ongoing support" through the province's biodiesel production incentive, a spokesman said in an email.
The biodiesel incentive provides 14 cents for every litre of biodiesel produced in Manitoba until March 2015.
The provincial government also licensed the facility under the Environmental Act, which is "intended to mitigate impacts to the environment" such as chemical spills, waste water, air pollution and noise, according to a spokesman.