Firefighters were still battling a stubborn blaze Saturday evening at an Oshawa industrial complex that forced the evacuation of several buildings earlier in the day.

No injuries have been reported from the fire at McAsphalt Industries Limited on Farewell Street, south of Harbour Road.

Businesses neighbouring the plant were evacuated after the blaze began at about 5:30 a.m.

Firefighters thought they had the fire under control around 9 a.m., but it spread to other parts of the building, causing a partial collapse.

Saturday evening, nine trucks and nearly 40 firefighters were still working to extinguish the large fire.

Oshawa Chief Fire Prevention Officer Susan King told CTV News Channel the plant contains a number of rubber and plastic products, which prompted fears that the dense smoke billowing from the fire could be carcinogenic.

However, King said there is always a risk whenever a fire produces a significant amount of smoke. Residents in the surrounding area have been urged to stay indoors and keep their windows and doors shut.

“Any smoke is not healthy so we just want to make sure that people remain safe,” she said.

Residents a few kilometres away from the fire said they didn’t realize how severe the blaze was until police knocked on their door.

“They just said the toxic fumes are bad so stay inside, keep your doors and windows closed,” said Matt Baszczynski.

Around 10 businesses have been evacuated on Colonel Sam Drive as a result of the fire, including the headquarters for General Motors Canada.

The Ministry of Environment was also on scene Saturday evening to ensure that none of the potentially toxic runoff from water poured on the building would travel to the nearby Oshawa harbour.

Oshawa Port Authority issued a statement Saturday saying it would be working with McAsphalt, fire officials and the ministry on the cleanup, air quality and water analysis.

King estimates fire crews will continue extinguishing the blaze late into Saturday and possibly into Sunday. She said firefighters will be checking for any hot spots and making sure the fire does not rekindle.