The Office of the Fire Marshal is investigating after two "suspicious" blazes razed two structures overnight in Oshawa.

Flames could be seen for blocks away after a four-storey wooden structure, which was under construction, caught fire on Bloor Street West near Burton Road.

"I got poked in the back, my son woke me up and told me I had to leave," said neighbour Dave Jump. "The next thing I know, I have a cop at the door. 'Bang, bang, bang.' And he wouldn't stop banging until I got to the door."

Right next door, Peter Sutcliffe says he awoke to bright red flames outside his window around 2:30 a.m. He tells CTV News he sustained burns on his left arm after he pushed his front door open to evacuate.

"That was the amount of extreme heat, and that was just a split second. I never even thought about it, I just touched it like I normally do," he said.

Sutcliffe’s roommate, Danielle Ledrew, said she could feel the heat migrating to their home.

"That’s when you definitely got scared," Ledrew said.

Platoon Chief Warren Lesser, of the Oshawa Fire Department, says this was a five-alarm blaze. He says nearly all of the city's firefighters were called into action and Durham Regional Police also helped in evacuation efforts.

"This is probably the most alarms you can have here in Oshawa. We had almost every apparatus at this call. Then we were diverted to another fire, not too far from here, which we called for help from Whitby and Clarington."

The other fire, which officials say may be linked, was just half a kilometre away. That blaze is believed to have started in a garage before it spread to a neighbouring business.

Mike Foley, whose family owns and operates Woodland Homes and The Foley Group, says three generations of Foleys currently operate businesses in the building badly damaged by the fire. He said investigators told him they believe embers from the first fire landed on the plastic tarpaulin of a neighbour's garage roof, which then ignited.

"My dad, John Foley, he's still living, he built this building in 1960, so we have a lot of memories here,” he said.

"A lot of family works here, in a bunch of different businesses, but they worked here for years and years and years. So yeah, it's a lot of history gone. It's sad," his wife Jill Foley said.

Fire officials, who are calling the original blaze "suspicious," said cinders travelled as far as two kilometres.

"Because of the intensity of the fire, how far it was along when we arrived, some accelerant must have been used," Platoon Chief Lesser said.

Jump, whose house was for sale but is now so damaged he has been forced to take it off the market, said he would be very disappointed to learn that someone set this fire deliberately.

"Don't let me catch you. I'd like to find out where you are and put you in jail," he said.

Investigators from the Office of the Fire Marshal tell CTV News they hope that to complete their investigation by Monday.