Drivers and businesses are being urged to do their bit to try to prevent thefts from vehicles.
A catalytic converter valued at £1,500 was removed from a Mercedes van in Ronald Road, Halstead last week.
PC Chris Philpott said: “It is quick and silent and it only takes 30 seconds to remove a catalytic converter, so it is difficult to stop.
“We do constant foot patrols, but it would be nice to see companies trying to look at things to help deal with it.”
Anybody with information is asked to call Essex Police on 101 or Crimestoppers on 0800 555 111.