A mysterious vacation tragedy became a criminal case Wednesday with the arrests of three people in the deaths of four Montrealers whose car plunged into a canal near Kingston, Ont.

A source familiar with the investigation told CTV News that Kingston police officers came to Montreal to make the arrests Wednesday morning, and that the suspects were to return to Ontario in order for the case to proceed.

Zainab Shafi, 19, sisters Sahar, 17, and Geeti, 13, and their aunt Rona Amir Mohammed, 50, all died on June 30 when their car drove into a lock near Kingston. The family was coming back from a trip in Toronto.

Police would not confirm reports that the three suspects are Shafi family members. Kingston police would only say in a statement that there has been a "change in the status of this ongoing investigation" and that they would provide more details at a news conference on Thursday at 2 p.m.

There are reports that two men and a woman, presumably family members, were arrested on their way to Trudeau airport.

Neighbours have confirmed that police were at the Shafi house in St. Leonard for several hours on Tuesday night. One neighbour also said he saw the dead girls's father, his wife and their little boy leave the unit in a van on Wednesday morning along with another man. By Wednesday evening, the van in which they left was back in the driveway of the vacated home.

Surprised

Joyce Gilbert was surprised to hear that arrests have been made in the case.

"We are shocked to hear that someone here is involved with the deaths," said Gilbert.

Mystery

The women were found at the bottom of the Rideau Canal's lock in Kingston Mills and investigators originally described their deaths as "suspicious,'' although no evidence of foul play was disclosed.

Police were baffled by how the car left the road and ended up in three metres of water in the lock, which would be difficult for a car to access. At the time, police said they weren't certain who was in the driver's seat but confirmed all four females were in the vehicle when it was recovered.

Rebellious

After the deaths of the four women, Mohammed Shafi and his wife Tobba Yahya told CTV News that Zainab was rebellious, and had a habit of taking one of the family's cars without permission despite not having a driver's license.

They also said they left Afghanistan in hopes of finding a better life in Canada.