Police have issued advice to motorists following a number of thefts from motor vehicles parked at an M40 service station.
There have been 28 thefts reported from motorists whose vehicles were parked in an Oxford service station between May 1, and June 30.
The offenders gained entry to the vehicles without causing any damage and stole items from the boot while the motorist was inside the service station.
Sergeant Neil Anns said: “We have seen an increase in vehicle crime offending taking place at service stations, often victims are locking their belongings in the boot of the car and leaving the vehicle unattended for no more than five minutes.
"In that time, the vehicle is being entered and items are being stolen, we have cause to believe that ‘Jamming’ devices are being used.
“When the ‘Jamming’ device is switched on, the device will block the signal from the motorist’s vehicle key, preventing the vehicle from locking and allowing the offender to have access.
“Using such a device is illegal under the Wireless Telegraphy Act 2006.
“Our advice for motorists stopping at motorway service stations across the county is 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.
"We also advise you to remove belongings from your vehicle to prevent loss of property.
“Please do not approach these individuals. Instead you should report any suspicious activity to police immediately by dialling 999.
"Alternatively, you can report information anonymously to Crimestoppers on 0800 555 111.”