SUPERMARKET staff contacted police amid fears crooks were using an electronic jamming device to stop customers locking their cars.

Shoppers reported the problem at Tesco, in Highwoods, Colchester.

Laura Ward, from St John’s, Colchester, said she and partner, Richard Wingar, had experienced problems locking their car when at the store in the past two weeks.

Ms Ward, 25, said: “I had to keylock it in the end and I just put it down to it not working.

“It was really strange, especially as I’d only just put a new battery in the electronic key and it worked at home.

“Now I know what might have caused it, I hope it deters criminals and urges other people to double-check their car is locked.”

Criminals use jamming devices to block the signal from remote key fobs, and steal the car or items from the vehicle.

A Tesco spokesman said: “We were very concerned to learn of this issue and immediately alerted the police.

“Staff regularly patrol the car park and we will be helping the police with their investigation in any way we can.”

Police have advised motorists to ensure their cars are locked and not to rely on electronic key fobs.

A spokesman said: “Police have had reports from people in the Tesco car park in Highwoods Square unable to open their car doors with the electronic key.

“The suggestion is someone in the area is using some sort of jamming device. We are monitoring the situation, but there is no evidence of any criminal intent.”