A fire that gutted four homes has caused $1.5 million in damage.

Fire investigators say they now believe the massive blaze started in the backyard of one of the homes that was completely destroyed by flames. The exact cause of the fire remains unknown at this point. 

"We're focusing our efforts on the second home in from the corner, at the back of the house," said Sylvan Lake Fire Chief Cliff Brausen.

Firefighters got the initial call around 5 p.m. Tuesday, but when volunteer crews from the area arrived, the damage was done.

"When we pulled up on scene we had three fully involved single family dwellings, flames impinging on the fourth structure," said Brausen.

Brausen says there was nothing fire crews could do to save the properties; instead they focused their efforts on the fourth structure.

It took 35 firefighters over an hour to gain control of the blaze.

Amanda Miller's family home was destroyed by the fire. She tells CTV News her brother was inside the home when the blaze started.

"My brother barely got out. The propane tank on the deck exploded when he was in the kitchen trying to pour water to put out the deck," she said.

Several other homes were badly damaged by the fire as well.

Fire officials say the heat was so intense that siding on houses located across the street melted off. Fire investigator Frank Harris says there has never been a more destructive fire in Sylvan Lake.

"I've been here 25 years and this is the largest [fire] I've seen," said Frank

Local Red Cross volunteers are now working in the area to provide shelter, food and clothing to those affected by the fire.

With files from Adam Kuzina