Motorists are being warned about the growing number of thieves who are targeting catalytic converters.
The converters control and convert emissions into less harmful substances.
Thieves want the converters because they contain precious metals such as platinum and palladium, which are of high value.
If ripped out from underneath a vehicle, the owner could be left with a repair bill running in to thousands.
Motorists would be able to tell that their converter had been taken because the engine would make a different noise.
Police are urging people to fit special alarms to their vehicles which can be triggered when the converter is removed.