People are being warned not to risk travelling in illegal taxis.
It's after a driver was arrested for operating an unlicensed taxi in Derry city centre over the weekend.
The driver was interviewed and later reported to the Public Prosecution Service.
A spokesperson for the PSNI said:
"We would ask you to be vigilant when using taxis in the city and check that they are displaying Taxi licence plates. If they are not, don't get in it.
"Travelling in an illegal taxi could place you at risk."