A right foot was found by hikers in Hewick Meadows Park on Wednesday and police found a severed head a day later.
On Friday, two hands were found in the Credit River, which flows through the park.
Peel Region Police, which are responsible for the area that includes Mississauga, have yet to confirm the body parts are from one person.
Investigators believe the remains are female because the foot had yellow painted toenails.
Peel Const. George Tudos said Sunday that the ground search was being aided by cadaver dogs and a dive team.
They're hopeful of finding evidence or the remaining body parts, but Tudos admits the search would take at least a few days to complete.
Meanwhile, police are also investigating after remains were found in east Toronto, but it has not been confirmed whether those remains are human.
Police are waiting to hear from the Ontario coroner's office and Toronto police Const. Wendy Drummond says she didn't expect the results of the coroner's review on Sunday.
Toronto police contacted Peel police Saturday to notify them of the find, but it was not known if the two discoveries were linked.
Several local media outlets reported that a bag containing what appeared to be remains was discovered Sunday near the site in east Toronto where Saturday's remains were found.
But police were quoted as saying it was unknown whether Sunday's discovery was human remains.