The catalytic converter turns toxic chemicals in the exhaust of an internal combustion engine into less toxic substances.
Thieves have stolen at least six catalytic converters from vehicles at a business in Lincoln overnight on Tuesday, March 13.
The incident took place at a business in Sadler Road and is the latest in a spite of similar thefts across the county, Lincolnshire Police warns.
Officers believe at this stage that at least six converters were stolen from Mercedes vans and an attempt was made to steal form a further six from the Sadler Road premises.
This follows another business in the road being targeted between March 9 and 12 when a further 10 cat converters were stolen from vehicles.
Police say this is a growing issue across the county and officers are urging companies with large fleets and car dealers to review their security.
Thieves are mainly targeting 4x4s and vans as it is easier for them to get underneath them to cut the converters off.
Firms are being urged to think about where and how they park their vehicles in terms of restricting access underneath.
They are also being urged to review and invest in their security lighting and alarms for their sites and to make sure that any security features are advertised on perimeter fencing or entrances to the sites.
Patrols are being increased in vulnerable areas and officers are asking the public to report any suspicious activity around vehicles as soon as possible.