Cassia Manor at Franklin Landing, an apartment complex in Fort McMurray, erupted in flames on Monday night just days after the first residents returned home to the beleaguered city.

The complex is located downtown, near Prairie Loop Boulevard and Franklin Avenue, which was clogged with emergency vehicles around 9 p.m. MT

The fire broke out around 8 p.m. Officials said it didn't appear to be related to the wildfire, although the cause was under investigation. No injuries were reported.

Bob Couture, of the Regional Municipality of Wood Buffalo, said the fire was contained and under control while emergency crews continue to fight the blaze.

June 6 8:39pm. A message from Bob Couture on the structure fire downtown <a href="https://twitter.com/hashtag/ymm?src=hash">#ymm</a> <a href="https://t.co/FXYk7FZlH9">pic.twitter.com/FXYk7FZlH9</a> —@RMWoodBuffalo

Mitchell Hurst, of Thunder Bay, Ont., has been in Fort McMurray for three weeks doing restoration work on smoke damaged buildings, and helping to clean up the wildfire wreckage in some of the worst-hit neighbourhoods.

He was taking a break for dinner, when a plume of thick black smoke from the downtown apartment building came into view.

He pulled over and decided to help by alerting residents about the approaching flames.

"I decided to pull the fire alarm in the building right next to it, so I jumped the fence and went inside, but there was no fire alarm to pull in the front entryway, and all the doors were locked, so I yelled 'fire' a few times and got out of there.

"By the time I got outside, there were flames shooting out from the roof."

Within minutes, emergency vehicles arrived onto the scene, but Hurst said the building was fully engulfed.

"I was 20 feet away and I could feel the heat of the flames inside my car," he said.

'Icing on the cake'

Although Hurst was shaken by what he saw, his thoughts were with the affected tenants and the city.

"We work in fires all the time, I mean, that's why we're here, but I've never seen one that close.

"I just, I felt bad for the people living in those buildings. The city has already had enough traumatic events recently. This is just icing on the cake."

Katmbo Kasinyabo had only been back in the city for two days after being evacuated to Edmonton during the wildfire. He watched the flames from the street.

"I just come again in my mind that we are going to be evacuated, because that's what happened last time," he said. "We just rush to see what's going on, to be prepared to go. That was my first impression."

He said it was too soon to see flames after the wildfire that ripped through the area.