Acting Senior Sergeant Ian Temple, of Dunedin, said it appeared two vehicles had been racing up Wray St, in Brockville, before being joined by a third in nearby McCurdy St.
Two of the cars collided as they turned into Saunders St, leaving a pregnant woman aged in her 20s - a back seat passenger in one of the vehicles - needing medical attention, he said.
The woman had ''no obvious injuries'' but was taken to Dunedin Hospital for a check up, Snr Sgt Temple said.
A shocked resident of the Brockville street told the Otago Daily Times she saw a black vehicle ''hooning'' all over the road before hearing a massive bang.
''It was bloody scary. He had no control over that vehicle.''
Tyre marks stretching more than a 100m were visible on Wray St following the crash, which occurred about 3.20pm yesterday.
One of the first people at the scene said she saw a man emerge from one of the crashed vehicles helping a ''very upset'' woman.
The man told her the woman was pregnant, and so she helped to keep her calm with breathing exercises as they waited for an ambulance to arrive, she said.
The driver of the other crashed vehicle ''just took off'', with one of the car's front doors still open, she said.
Other witnesses said they saw the car being driven into a driveway at a nearby McCurdy St property and police later visited the house.
A McCurdy St resident said boy racers were a frequent problem in the area. Snr Sgt Temple said police were unsure how many occupants had been in each of the cars, and no arrests had yet been made.
Inquiries to identify the drivers involved were continuing, and anyone with information was asked to contact Dunedin police on 471 4800, or anonymously via Crimestoppers on 0800 555 111.
