Investigators say arson was behind the massive blaze that tore through a south Edmonton condo development last month.

More than 80 firefighters were called out to the Rutherford Landing development near 119th Street and 21st Avenue on Sept. 29, but were unable to stop the fire from spreading, destroying all three condos under construction.

All three buildings were levelled by the blaze, causing $20 million in damages making it one of the costliest fires in Edmonton history, according to the city.

"The initial onset of the fire was quite huge," said fire investigator Capt. Shayne Page. "So base on that, yes, it caused the fire to spread quickly."

Fire investigators aren't revealing what caused the fire but say it started in the east building.

Fire Rescue is working with arson detectives to investigate the blaze. There are no suspects and investigators have no leads. 

The heat of the fire caused the front of Felix Vizcarra's house to completely melt off.

"It's kind of unfair," he said. "'Cause most of us now are just living not with insurance coverage. Like I'm paying for a hotel right now."

Fire officials say about a third of all fires in Edmonton are deliberately set.

In 2012 alone, there were 204 reported arson fires, resulting in $23 million in damages.