Cars had been stolen from central and north Dunedin.
Two vehicles were found dumped at Outram Glen on Wednesday.
One, a Nissan Primera, was driven into the Taieri River and the other, a Nissan Sentra, was abandoned on the banks of the river at Outram Glen.
They appeared to be stolen solely for the thief to enjoy a joyride, acting Snr Sgt Thomson said.
A guitar had been taken from one of the eight vehicles, but the modus operandi did not appear to be targeting the vehicles for possessions or parts.
"People or a person are targeting Nissan motor vehicles. Whether they have a key, or how they are entering them, I'm not sure," he said.
"We ask if you have this type of vehicle to keep them locked."
- Otago Daily Times