Peel Regional Police's Public Safety Unit, a unit of officers who are trained in the search for lost persons and the search for evidence, were on scene most of the day searching for “evidence of foul play,” two police sources confirmed.

Peel police Chief Jennifer Evans confirmed Wednesday that evidence was found at the scene, including pieces of paper with information on it, that police are following up on. Police have their Forensic Identification Unit at the scene, and they are working with fire investigators to try to determine the cause.

Police were asking that anyone who has found "suspicious property" to turn it over to police.

Tuesday night, a man talked about handwritten letters he said a friend recovered on the street immediately following the blast, according to The Star.

According to a text message conversation with The Star, the pieces of paper were found on the street in front of the destroyed house, put in a grocery bag and handed to police.

"Dear God, as of next week everything will fall apart for us," begins the note.

It goes on to say: "We owe mortgage, company, house taxes, water bill, gas bill, hydro bill" and "our outside looks like crap, unkept lawn, overgrown plants, bricks on wall cracking."

The note concludes: "The upstairs bathroom electricity is off, the back bathroom shower has problems and we have No Money to fix or pay anyone."

The note's author is unknown. It is also unclear whether it is related to the explosion.

Peel Sgt. Josh Colley said police are trying to gather as much information as possible at the blast site.

“As you know, there were lots of damaged homes. Every bit of documentation, everything found in the area, we’re going to treat as serious,” he said.

Officials working on site have deemed that some residents can now return to their homes as the perimeter has been further reduced, the City of Mississauga said Wednesday night. Displaced residents need to call Peel Regional Police at 905-453-3311 ext. 1241 to find out if they are free to return to their homes. Residents that are allowed back to the area will be able to access their property either on foot or in their vehicle.

- with files from Pam Douglas