Ontario’s police watchdog is investigating after four people were taken to hospital with serious injuries following a vehicle rollover in Brampton early Monday morning.

Police said it happened on Torbram Road north of Sandalwood Parkway East at 2:50 a.m.

Four adult male occupants of the vehicle were taken to hospital after the incident with what paramedics told CP24 are serious injuries.

It’s unclear what led to the rollover or if another vehicle was involved. It’s also unclear why the province’s Special Investigation’s Unit (SIU) is investigating the incident.

The SIU is a civilian law enforcement agency, independent of the police, that conducts criminal investigations into circumstances involving police and civilians that have resulted in serious injury, death or allegations of sexual assault.

Images from the scene show what appears to be an SUV and an attached camper trailer both flipped on their sides.

Torbram Road will remain closed in both directions near the site of the crash while the SIU continues to investigate. Motorists are asked to use alternative routes.