Thieves take 34 catalytic converters since 1 December
Over the past six weeks 34 catalytic converters containing valuable metals such as platinum and rhodium have been stolen from vehicles in Suffolk.
Thieves are targeting commercial vehicles and vans in car parks, lay-bys, driveways and on the street.
Police are visiting scrap metal dealers across the county to ensure checks are made on all metals brought for sale.
Thefts since 1 December have been increasing, police said.
Drivers are advised to take precautions to keep their vehicles secure.
Bernard Plume, from Suffolk Police, said: "Vehicles should be kept in a well-secured garage where possible, and if no garage is available, in a well-lit, public area.
"Commercial vehicles should also be kept in a locked building or compound. Use alarms, lighting and CCTV to deter thieves."
The converter should also be etched with an identity or marked with Smartwater, he said.