The fire is believed to have started in a trash can behind the building, located in the Abbottsfield area near 34th Street and 118th Avenue, just before 3 p.m.
"The garbage can was on fire and when the fire department got here it quickly spread and it got into the roof," said area resident Brian Berezanski.
Other witnesses say they actually saw a group of people hanging out behind the former McDonald's restaurant shortly before the fire.
"They were drinking and celebrating Canada day and I'm not sure what it was they threw into the garbage in the back, but I think it was a bottle of something on fire," said witness Dylan Fenn.
There have been no reports of injuries and no damage estimate has been released.
In a release, Melanie Pope, Police Information Officer for Edmonton Fire Rescue Services, confirmed that the fire was deliberately set, with the file being turned over to police.
Police are asking motorists to avoid the area while firefighters work to put out the blaze.
