The two grandparents killed along with their infant grandson in a wrong-way highway crash with a van being chased by police were visiting from India, Ontario’s police watchdog said Thursday, while the baby’s parents were also in the car but survived.

The Special Investigations Unit said the three-month-old boy’s father and mother, who live in Ajax, Ont., were treated in hospital after Monday’s crash. The watchdog said the 27-year-old mother was treated for serious injuries but offered no further details about the 33-year-old father’s condition.

The crash has raised questions about the police decision to pursue a suspect van in an alleged liquor store robbery into oncoming traffic on one of Canada’s busiest highways.

Durham Region police gave chase on Monday to a cargo van identified as a vehicle of interest in an alleged LCBO robbery shortly before 8 p.m. in Clarington, Ont.

The SIU said the pursuit of the van shifted to the 401, where the van went into oncoming traffic and collided with the family’s sedan.

The driver of the van, who was also killed in the crash, was identified by SIU on Thursday as a 21-year-old man. A passenger in the van, a 38-year-old man, was sent to hospital with serious injuries, SIU said.

The SIU said the grandparents who died were a 60-year-old man and 55-year-old woman.

READ MORE: Grandparents, grandchild among 4 dead in wrong-way 401 pursuit crash

In a written statement Thursday, Ajax Mayor Shaun Collier called the crash an “unthinkable tragedy.”

“It is with deep sadness that I offer my condolences to the Ajax family shattered by Monday’s horrific crash on Highway 401,” he said.

The SIU – which is investigating the crash and what led up to it, including the police pursuit – said two subject officials and four witness officials have been designated as part of its probe.

All post-mortems in the case took place on Wednesday, the SIU said.

Durham Region police said Tuesday that the incident “has had a profound impact” on its community and members.

“We understand there are many questions, however there is a legislated process regarding investigations conducted by the SIU that our service must adhere to,” it wrote. “DRPS is fully cooperating with the SIU and as such are unable to make a public statement on this incident.”

This report by The Canadian Press was first published May 2, 2024.