Kingston police are investigating the mysterious deaths of a 50-year-old woman and three teenaged sisters from Quebec, who were found in a submerged car Tuesday morning in the Kingston Mills locks, northeast of Kingston, Ont.

The sisters were aged 13, 17, and 19, and the woman in her 50s was a relative, according to Kingston police Const. Mike Menor.

Menor could not confirm the exact relationship between the woman and the three sisters, nor could he confirm reports that they were from St. Leonard.

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

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

"It's very tragic...very, very strange," said Menor. "It's a really weird spot where the car was. It's not a spot where you would drive."

Police believe the car went into the water sometime between midnight Monday and 6 am Tuesday, and are asking for help from anyone who may have seen the car around that time.

So far, no witnesses have come forward.

Autopsies expected Wednesday

It took police divers and cranes more than two hours to retrieve the bodies and the vehicle.

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

The car will undergo a mechanical inspection and autopsies will be performed on the victims on Wednesday, Menor added.

He said the bodies have been identified, but names will not be released until all family members have been notified.

It is believed that the victims had been visiting relatives in Ontario and were on their way back to Quebec.

With files from CTV Ottawa