Two men have been killed in a car crash during a police chase.
The vehicle hit a road barrier on Bradford Road in Brighouse, West Yorkshire, just after 01:00 BST as it fled from officers.
Two men, thought to be in their 20s, died as a result of their injuries, the police watchdog said.
The Independent Office for Police Conduct (IOPC) has launched an investigation after a mandatory referral from the West Yorkshire force.
In a statement, Miranda Biddle, of the IOPC, said it had taken statements from two officers.
“Our role is to establish and examine the circumstances of what happened,” she said.
“This work is already under way, and West Yorkshire Police is cooperating fully with our inquiries.”
Earlier, the force said: “At 01:07 a car containing two male occupants was involved in a collision in Bradford Road, in Brighouse town centre.
“Due to the involvement of a police vehicle in the circumstances leading up to the collision, the incident has been referred to the Independent Office for Police Conduct.”