Police are warning motorists to make sure their vehicle is locked when they park at motorway service stations, following a series of thefts.
Thames Valley Police said that 23 thefts were reported from motorists whose vehicles were parked in three services in Berkshire -- Reading, Chieveley and Membury --between 1 May and 31 May.
The offenders gained entry to the vehicles without causing any damage and stole items from the boot while the occupants were inside the service station.
Sergeant Alan Hawkett, from the Neighbourhood Policing Team at Newbury Police Station, said: "Following the arrest of two men earlier this year, we have intelligence to suggest that a jamming device is being used to commit these offences.
"When switched on, the device will block the signal from the motorist's vehicle key, preventing the vehicle from locking and allowing the criminal to have access."
He advised motorists stopping at motorway service stations to look and listen for confirmation that their vehicle has locked before walking away from it.
"You should manually check the door handle after attempting to lock your car and never leave any valuables in the vehicle. If you are not able to lock your vehicle using your key remote, please do not leave it unattended, as this could be a sign that a jammer is being used nearby."
Any suspicious activity should be reported to police immediately by dialling 999.
Do you double-check to make sure your car is locked?