A quantity of cash was stolen from a taxi while it was parked in Balfour Street, Blyth.
Thieves broke into the vehicle sometime between noon on Monday, May 6, and 8am the following day.
Investigating officers believe the thieves searched the car and stole a number of bags containing cash.
Officers are appealing for anyone that saw anything suspicious in the area around the time of the theft to contact them.
Taxi drivers are being advised to remove their takings every time they leave their vehicles unattended and ensure they are locked.
Anyone with information should contact police on 101 ext 69191.