KINGSTON, Ont. - It could be weeks before the results are released from the autopsies on the bodies of four Montreal residents pulled from a lock in Kingston, Ont., police said Thursday.

Investigators are baffled over how the car left the roadway and ended up underwater and hope the autopsies, scheduled for Thursday in Ottawa, will shed some light, said Kingston police Const. Michael Menor.

There are no obvious tire tracks to indicate what happened and the deaths are being treated as suspicious until the investigation proves otherwise, he said.

"We're waiting with bated breath here," said Menor, who added it could be days or weeks before the results are released.

The bodies of three teens, aged 13, 17 and 19, were found along with a 50-year-old woman, described only as a relative, inside a vehicle that was submerged in the northernmost lock at Kingston Mills, northeast of Kingston, on Tuesday.

The group had been on vacation in southern Ontario and were on their way back to Quebec, said police in Kingston, about 260 kilometres east of Toronto.

Montreal police said Thursday they received a request from Kingston police to locate a second vehicle in the city's north-end St-Leonard borough.

Montreal police spokesman Daniel Lacoursiere would not say whether officers had found the vehicle. He also wouldn't confirm reports that the second vehicle may have been seen with one of the victims in Kingston.

A lockmaster for Parks Canada discovered the car, which witnesses say was a newer-model Nissan, about 10 metres from the doors of the Kingston Mills Locks about 9:30 a.m. Tuesday when they were trying to open the doors for the day. An oil slick on the water caught the lockmaster's attention.

The case has left police puzzled as to how the car left the road, drove down a patch of grass - either over a concrete barrier or through a gate - and through two of the poles on the dock.

"It was there for a reason, it didn't drop out of the sky," Menor said. "It got there somehow. It's frustrating."

Investigators were not considering the possibility that the car entered the water from another location and was carried to the lock by a current, he added.

As part of the probe, police have turned the car over to mechanics to see whether there was a breakdown, or if other forensic evidence can be found that might help investigators discover what happened.

Menor said he was waiting to get clearance to release the names of the victims after holding them back while police tried to contact family members.

"We can't imagine the pain ... it's beyond heart-breaking," he said.

"I just wish we could go back in time and change things. ... These were three beautiful sisters."

-With files from Andy Blatchford in Montreal.