West Midlands Police has referred itself to the official watchdog after officers failed to stop a speeding car before a crash in which three people were injured.
A BMW collided with a tree in Handsworth, Birmingham, in the early hours of Monday 2 October.
Police had already spotted the vehicle which was said to be "travelling at speed" a short time before it crashed on Island Road, close to the junction of Lawnswood Grove, at around 2.15am.
Two male victims managed to climb out of the car by the time the emergency services arrived.
Three ambulances, two paramedic officers, a MERIT trauma doctor, a critical care paramedic and the Hazardous Area Response Team attended the scene.
A 29-year-old man was given advanced trauma care for serious injuries before he was taken to University Hospitals. He remains in a critical condition.
The second seriously wounded male was taken to the same hospital.
A woman was transferred to Sandwell Hospital for further treatment after managing to escape the wreckage.
West Midlands Police said the collision was "serious" and has reported the incident to the Independent Office for Police Conduct (IOPC).
The force said it was after: "The vehicle was spotted by officers and was believed to be travelling at speed a short time before the collision."
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