All four people were pronounced dead at the scene on Highway 401 in Whitby, about 50 kilometres east of Toronto, police said.

Ontario’s Special Investigations Unit (SIU) in a statement on Thursday said that two of the victims, a 60-year-old man and a 55-year-old woman, were visiting from India.

SIU did not release the names of the victims.

The couple’s three-month-old grandson also died in the multi-vehicle collision, which closed Highway 401 for several hours on Monday, it said.

The agency said that the parents of the infant, his 33-year-old father and 27-year-old mother, were travelling in the same vehicle and were taken to hospital.

The mother’s injuries are serious, the SIU said.

The robbery suspect was also killed in the collision, which involved at least six vehicles.

Officials have said the deadly car chase started with a liquor store robbery in Bowmanville and ended around 20 minutes later after the suspect in a cargo van led Durham police on a high-speed chase against opposing traffic on Highway 401.

A 38-year-old male passenger from the cargo van was also taken to the hospital to be treated for serious injuries.

The autopsies for the victims all happened in Toronto on Wednesday.

Seven investigators, one forensic investigator and one collision reconstructionist continue to investigate this case, the statement said.

The SIU is an agency called in to investigate whenever police are involved in a death, serious injury or allegations of sexual assault.