Flowers sit near the Kingston Mills locks on the Rideau Canal where four Montrealers died on June 30. Flowers sit near the Kingston Mills locks on the Rideau Canal where four Montrealers died on June 30. (Sunny Freeman/Canadian Press)

Police have made arrests in connection with the mysterious deaths of three Montreal sisters and their older female relative, whose car was found in late June submerged in water near a Rideau Canal lock in Kingston, Ont., CBC News learned Wednesday.

Police said they will make a further announcement about the case at 2 p.m. ET Thursday at Kingston police headquarters. No further details have been released.

Tooba Mohammad Yehya weeps as she and her husband, Mohammad Shafi, speak to reporters on July 3 at their home in Montreal about the loss of their children.Tooba Mohammad Yehya weeps as she and her husband, Mohammad Shafi, speak to reporters on July 3 at their home in Montreal about the loss of their children. (Peter McCabe/Canadian Press)

Zainab Shafia, 19, Sahar Shafia, 17, Geeti Shafia, 13, were found in the car with relative Rona Amir Mohammed, 50, when the vehicle was discovered under water around 4 p.m. on June 30.

All four were from St-Léonard, Que., and had been reported missing by relatives.

The sisters' mother, Tooba Mohammad Yehya, said the family had stopped in Kingston on their way back from Niagara Falls, driving in two cars.

Yehya, who has four other children, said Zainab Shafia had taken the keys to one of the cars, saying she wanted to get some clothes from the vehicle.

After Shafia took the keys, Yehya said she didn't know what happened except that one of the family's cars was taken out overnight.

She said Shafia had driven a few times, but was not an experienced driver.