Investigators with the Office of the Fire Marshal are expected to be at the scene today of a massive fire at a food processing plant in Burlington.

The three-alarm fire broke out at Paletta International, a food processing plant located near the Queen Elizabeth Way and Appleby Line, shortly after 4 p.m. Wednesday.

At the height of the fire, 40 firefighters and 14 trucks from three different cities were on scene battling the blaze.

“We originally had both Hamilton and Oakville assisting us, however, they have both returned to their cities and it is only Burlington units on scene currently,” Burlington Fire Platoon Chief Dennis Hayes told CP24 on Thursday morning.

“The roof collapsed quite early on in the fire and we’re just continuing to pour water onto hotspots. We are working very hard currently to get as much water in there as we can to cool it, however, we are going to have to bring in heavy machinery through the day to be able to break that down and get inside there.”

No injuries were reported and all staff members at the plant have been accounted for.

The cause of the fire has not yet been released.

“The employees were in the building at the time. Unfortunately due to the size of the fire and our activities, we weren’t able to interview any of them and they have since left the scene,” Hayes said.

“We will have to wait till they get back in today and talk to some of those employees and see if they can give us some more information.”

The Office of the Fire Marshal has been notified and is expected to attend the scene at some point on Thursday.

Speaking to CP24 Thursday, Burlington Fire Chief Dave Lazenby said there are some concerns about dangerous materials inside the building, including ammonia.

“The Ministry of the Environment was here and we also had Halton Region looking at things like water runoff and things like that,” Lazenby said.

Air quality tests have been conducted and Lazenby said no dangerous fumes have been detected.

“For a period of time, in the initial stages of the incident when the smoke was bad, we asked people to shelter in place in the neighbouring offices just to make sure people didn’t come out to difficult smoke conditions,” he added.

Lazenby said his crews will likely be on scene for most of the day.

“I don’t know how long the Ontario Fire Marshal’s Office will be here. It’s a significant fire scene that they dealing with,” he said. “It might take some time.”

Several roads were shut down following the fire but on Thursday morning, as crews became concerned that drifting smoke would cloud drivers’ visibility on the nearby QEW.

Police confirmed that all major roads in the area of Appleby Line and the QEW have reopened, including the QEW’s Toronto-bound ramps to Appleby Line.

Crews worked late into the evening to get the fire under control. The blaze was still considered active as late as midnight on Thursday

Tim Dyson, who works across the street from the Paletta International Corp. building, said he noticed the smoke just as he was clocking out for the night.

“It started getting heavier and heavier, and then we heard the sirens coming,” he said. “Then we realized what was actually happening.”

At its peak, the fire consumed 50 per cent of the building.

“The crews did an amazing job protecting the west end of the building and the systems in place there,” Lazenby said. “We’re going to work with the Ontario Fire Marshal to make sure it is safe for them to do their investigation.