Two women were killed on June 23 when the roof of the Algo Centre Mall caved in and plummeted two floors down into the building.
The provincial police force was assisting the Ontario Chief Coroner's office in its investigation into the deaths of Doloris Perizzolo, 74, and Lucie Aylwin, 37, but "as a result of information obtained," the police said Tuesday they are now also looking into the collapse as a criminal investigation.
Ontario Premier Dalton McGuinty announced a public inquiry into the mall collapse Friday following public outcry about why search-and-rescue efforts were called off two days after the accident, only to be restarted hours later after an appeal from McGuinty.
Residents have since complained that the mall was in shabby condition before the cave-in and have questioned the speed at which rescuers tried to reach those trapped in the rubble.
The Ministry of Labour is also conducting an investigation, but has said its probe will not look into the cause of the collapse.
The ministry paid six visits to the mall over the last three years, the latest one being in January when it received a complaint about a leak in the rooftop parking garage.
The inspector went to the site and found it covered in snow, making it difficult to determine the origin of any leaks, a spokesman for Ontario Labour Minister Linda Jeffrey has said. The inspector found no health and safety violations and no orders were issued.
Perizzolo is set to be buried Wednesday at Woodlands Cemetery, located steps away from the waters of Elliot Lake in the western part of the city.
CORRECTION: An earlier version of this story had an incorrect age for Perizzolo. This version has been updated.