Police in Hertfordshire are warning plumbers not to store copper pipes in their vans overnight after a recent spate of thefts.
In recent weeks, vehicles have been targeted in Woodleigh Road and Queensway in Ledbury, and also in Tarrington.
Inspector Jim McLaughlin said: "We would like those who carry copper piping in their vehicles, and in particular roof-mounted van pipe tubes and pipe carriers, to take steps to protect themselves against thieves.
"It appears we have criminals travelling around the county and attempting to steal copper piping from vans and focusing on pipe tubes on unattended vans at night.
"Anyone who works with copper piping will know how expensive the metal is at the moment, it means thieves are willing to break into pipe tubes to steal seemingly small amounts of copper."
Items made of copper, as well as other materials such as lead and steel, have become an increasing target for theft because of the rising costs of these materials.