Police in west Cheshire have warned drivers that thieves are targeting catalytic converters and exhausts for their metal parts.
Five vehicles in Ellesmere Port, Winsford and Nantwich have had the parts stolen in the past month.
Det Sgt Paul Wilcock said vans were vulnerable as they are easier to get underneath than most cars.
He urged owners to check their vehicles regularly and put a security markings on catalytic converters.
Serial numbers can be etched on or they can be marked with a UV pen, making it more difficult for thieves to sell them on and easier for police to trace.
"We would also ask scrap metal dealers to be mindful if they are offered a catalytic converter or exhaust system and if in doubt contact police," Mr Wilcock added.