Police are scouring the area near a river west of Toronto after a human head and foot were found.
The foot appears to belong to a female, as the toenails were painted yellow, police said, but until pathology tests are done investigators cannot say if both the head and the foot are from the same person.
"Without a cause of death we can't call it homicide, but certainly foul play — there's definitely something amiss," said Acting Inspector Randy Cowan.
The size of the body parts do not suggest they are from a child, Insp. Cowan said.
The right foot was found in the Credit River near the Hewick Meadows Park by hikers and the police marine unit found the head later Thursday.
Police can't yet say if the body parts were placed there or were transported there by the water from some other point in the river, which flows from headwaters above the Niagara Escarpment to Lake Ontario.
On Thursday afternoon, half a dozen police cruisers and an underwater search and recovery truck were parked near yellow tape that blocked off part of the river that runs through the park. Search crews, divers and dogs were combing the area, and police expect to be on scene for at least two days. Investigators are also asking for the public's assistance.
"We're looking for anybody that has seen anything suspicious within the last couple of weeks," he said.
"We're also looking for people to be vigilant in the area if they're out walking and they happen to find something that causes them concern to give us a call."
The scene appears to be in a fairly isolated area, away from houses and beneath an overpass.
Mississauga resident Peter Fletcher said the park is quiet and very dark at night, adding that it's busiest during the day when bikers and hikers take to the trail.
"It's just incredible for these things to happen in Mississauga," Mr. Fletcher said.
Officers are sifting through missing person's reports, in case any have a link to the body parts, Insp. Cowan said.
"Typically in the region there are always a number of outstanding missing people," he said. "The majority of those return safely...We are going through those reports right now, reaching out to family members."
Investigators believe the body parts were severed in the past few weeks. The force's homicide and missing persons department are on the case, Insp. Cowan said.
With a report from Julianna Cummins