Ontario’s police watchdog has launched an investigation into a deadly collision in Milton back in March.

The two-vehicle collision happened near Sixth Line and Derry Road at around 3:20 a.m. on March 30.

Three individuals were pronounced dead at the scene.

The victims included an 18-year-old man from Milton and a 16-year-old female from Brampton, who were both travelling in the same vehicle. The other victim was a 26-year-old man from Milton who was travelling in the second vehicle.

Few details are known about the circumstances surrounding the collision or the nature of police involvement.

In a news release issued on Friday, the SIU said that it was notified about the case by Halton Regional Police on July 22 and opted to invoke its mandate “based on the information received.”

The SIU has designated two subject officials and six witness officials as part of its investigation.

The SIU is an arms-length agency that investigates any incident involving police and civilians that results in death, serious injury, or allegations of sexual assault.