An Edmonton explosion that killed four people and sent several others to hospital is now being treated as suspicious.

Deputy Police Chief Darryl Da Costa told reporters on Monday that homicide detectives have taken over the investigation.

He said there is thus far no evidence that the explosion was caused by a bomb or a drug lab, but said the investigation is continuing.

"We are treating it as suspicious and that's standard process for us in that the deaths are unexplained at this point," Da Costa said.

"Houses don't just explode. We're trying to find out what caused this explosion," he added.

Autopsies on the four victims will be carried out Tuesday.

CTV Edmonton identified two of the victims of the blast: Craig Huber and Brad Winter, who lived next door to the house that exploded. The identities of the two other victims, a man and a woman, are not yet known.

The blast rocked a north Edmonton neighbourhood early Sunday afternoon. One home was completely destroyed, two were damaged beyond repair and 26 others suffered some damage, CTV Edmonton's Bill Fortier reported.

Witnesses described hearing a huge explosion Sunday around 1:15 p.m. that reverberated across a 12-block radius and left residents scrambling for safety.

People who lived several blocks away from the site of the explosion described a powerful blast that knocked pictures off the walls and triggered small fires in the area.

Claudio Frigo, who lives just a few doors down from the site, said the blast "shook the whole house. I heard glass imploding, I heard my son screaming."

Frigo said he would like to know the cause. "It's kind of nerve-wracking thinking that a gas line went."

Officials said that teams of investigators will sift through the rubble to determine the exact extent of the damage, as well as which houses are safe to inhabit. About 40 people have been temporarily displaced from their homes.

"It won't just be one individual, there'll be a team to make sure the houses are safe," DaCosta said. "We're going to be very diligent in ensuring their houses are safe so they can get back to them as quickly as possible."

Home video submitted to CTV Edmonton showed a chaotic scene moments after the explosion, with at least one fire raging and residents running to help.

Matthew Gilbert is one of a number of local residents who are being hailed as heroes, after he ran to the home where Huber and Winter died.

"I went into the house and it looked like the front entrance was hit by a train," Gilbert told CTV Edmonton.

Gilbert rescued a child from the home and returned to help carry out a woman.

City officials have said they are considering how to officially honour those who helped rescue the injured.

"Amazing," is what Mayor Stephen Mandel called the citizens who jumped in to help.

"You just can't believe how people just come to the fore when there are challenges like this. My understanding is that individuals were helping people get out from under rubble. Amazingly brave people."