The Independent Police Conduct Authority will investigate a police pursuit which ended in a dramatic crash in central Christchurch on Tuesday.
The collision resulted in a car smashing through the ground floor window of the Workbridge office building.
A 40-year-old woman driver had to be cut free of the the wreckage and was treated by ambulance staff at the scene. She was not seriously injured.
A pedestrian narrowly escaped being hit by the woman's car.
Police say the constable driving the unmarked police car had put his lights and siren on as he travelled through an intersection in pursuit of a motor scooter.
But he collided with the woman's car being driving along the Durham Street one-way system, and which witnesses say had the green light.
Wendy McIntosh and Stephanie Gainsford watched the incident and say the police car turned its lights and siren on just before the crash.
They say the officer involved in the crash immediately went to help the driver, while the motor scooter he had been chasing did not stop.
Police say the constable is a member of the Strategic Traffic Unit and is being interviewed by crash investigators.
Their findings will be referred to the Independent Police Conduct Authority for its own investigation.