w-edm-cp-8910971

Edmonton Police Service investigators comb through the rubble of the exploded home. ((John Ulan/Canadian Press))

Residents are trickling back to a north Edmonton neighbourhood after a massive blast left four people dead and damaged dozens of homes.

A house exploded at 91st Street and 180A Avenue Sunday afternoon at about 1:20 p.m. MT.

The blast damaged 28 homes and forced dozens of people to leave the area. 

About 10 families were allowed back into their homes Monday, but many others were waiting to hear if their homes had suffered serious structural damage.

Marg Whyte returned to her home Monday to find shattered glass and damaged pictures — but no major structural problems.

"I have a bit of damage to a wall and a door torn out," Whyte said. "That's minimal in the overall scheme of things."

The Red Cross is assisting families who were displaced by the blast, acting police chief Darryl da Costa said in a statement Monday.

Police search for cause

Investigators are still combing through the rubble, and officials said it could take days — or weeks — to pinpoint the cause of the blast, though police said Monday there is no indication the blast was caused by an explosive device or a drug lab.

David Checkel, an expert in gas explosions at the University of Alberta, said the cause of the blast is still a mystery.

"It could have been a gas explosion if something allowed enough gas to leak into the house to build up a substantial mixture of gas [and air]," Checkel said.

Friends have identified Brad Winter, 26, and Craig Huber, 30, as two of the victims. The two men lived next door to the house that exploded. Police have yet to identify the other two victims.

According to land titles, the house is owned by Dwayne Poirier and Jeanne Cathleen Heard. Their whereabouts at the time of the explosion are not known.

With files from CBC's Trisha Estabrooks