Four men in a BMW who were being followed by an unmarked police car have been killed in a road collision in Bradford, police say.
The Independent Office for Police Conduct (IOPC) has launched an investigation into the fatal crash, which occurred at 5.30am on Bingley Road at the junction with Toller Lane.
"It is understood, at this time, that the car was being followed by an unmarked police car at the time of the crash," the IOPC said in a statement.
IOPC regional director Miranda Biddle said: "This is a most tragic incident and our sympathies are with the family and friends of those who have died.
"West Yorkshire Police made a mandatory referral to the IOPC and at 6.24am we declared an independent investigation. Our investigators are attending post incident procedures, have travelled to the scene and have begun gathering evidence."
Police the road was likely to remain closed throughout most of Thursday.
Witnesses are reported to have described a loud bang and coming out to see a large amount of police activity with a number of cars involved in the crash.
Additional reporting by PA.
