Cars parked by hopeful owners at Oamaru's unofficial car sales yard at Awamoa Park were targeted by thieves on Saturday night.
Senior Constable Stu Hewett, of Oamaru, said three cars were broken into and one unlawfully taken on Saturday night or early yesterday.
He warned people about the danger of leaving vehicles in the Awamoa Park car park overnight.
Const Hewett said no items of any significance were stolen from the three cars, which had their windows smashed.
For decades, the car park next to State Highway 1 has been used by people to sell cars and other vehicles, including boats and caravans.
Most vehicles are removed at night.
