The four bodies found Tuesday in a submerged car northeast of Kingston, Ont. are those of a 50-year-old woman and three teenaged sisters from Quebec, according to police.

The black 2004 Nissan sedan with Quebec licence plates was submerged in about three metres of water in the northernmost Rideau Canal lock at Kingston Mills.

A Parks Canada employee made the discovery at the first set of lock doors after noticing an oil slick on the water.

"It's very tragic, very very strange," said Const. Michael Menor. "It's a really weird spot where the car was. It's not a spot where you would drive. There's lots of parking around."

Police divers and cranes needed than two hours to retrieve the bodies and the vehicle Tuesday afternoon.

The three sisters were 13, 17, and 19 years old and related to the 50-year-old woman, but police would not provide their identities or exact relationship until family members are notified.

Police have also not said whether foul play was involved. But the deaths continue to be treated as suspicious while the investigation continues.

Police are unsure of who was driving because the bodies were floating in the car when it was found.

"We have to really get into the forensics before we piece together how the vehicle went in and what movement it may have taken before it entered the water," said Staff Sgt. Chris Scott.

A houseboat owner told CTV Ottawa that he heard a loud noise between 2 a.m. and 3 a.m. Tuesday.

Autopsies are scheduled for Thursday in Ottawa. Anyone who may have seen the Nissan between midnight Monday and 8 a.m. Tuesday is asked to call Kingston Police.

With a report from CTV Ottawa's Jonathan Rotondo and files from CTV Montreal and The Canadian Press