The suitcase was found floating about 2½ kilometres from shore by two boaters, Toronto police said.
They towed it to shore at Bluffer's Park, in the city's east end. Police examined the contents and confirmed they were badly decomposed human remains.
A post-mortem examination is scheduled to take place on Thursday.
Police said it's too early to say whether Wednesday's discovery is related to the killing of Guang Hua Liu, whose body parts were discovered in east-end Toronto and Mississauga, Ont., in August. Liu's torso was not recovered by police.
Her former boyfriend Chun Qi Jiang has been arrested and charged with second-degree murder. Peel Regional Police are heading the investigation into Liu's killing and confirmed they are working with Toronto police to see if there is any connection between the Liu case and Wednesday's discovery of body parts.
Liu was reported missing on Aug. 11, one day after her friends dropped her off in front of a now-defunct spa she owned called the Forget Me Not Health Centre in east Toronto.
On Aug. 15, her right foot was found in the Credit River in Mississauga, Ont., about 45 kilometres west of her home.
Liu's head and hands were later discovered in the same river in the Hewick Meadows Park area. Days later, two calves, a thigh and an arm were found in West Highland Creek, just blocks from where she lived.
Forensic tests determined all the remains belonged to Liu, but police still do not know how she died.
Investigators are also still trying to determine where she died.
Police wouldn't provide further details on Wednesday on the torso that was found, but asked the public for help identifying the remains.
"We're in the early stages of our investigation so we're appealing to the public," said Toronto police Det. Les Dunkley.
Two other cases involving dismembered victims have made headlines in Canada this year.
In May, parts of a victim's body turned up in Ottawa, Vancouver and Montreal. Police would soon identify the victim as Jun Lin, an international student who had been studying at Montreal’s Concordia University.
His alleged killer, Luka Rocco Magnotta, was arrested in a Berlin café and subsequently extradited to Canada to face charges of first-degree murder, indignity to a human body and other criminal counts.Last week, a woman's torso was spotted . Police are still trying to identify the victim in that case. Suggest a correction