South Yorkshire Police have issued advice to drivers in the region in a bid to protect them against the use of car key jammers.
Detectives are urging drivers to check their doors are locked before leaving their vehicle, after a recent spate of thefts from cars with the use of electronic car key jammers.
Thieves have been using hand-held devices that block signals sent by drivers to lock their vehicles, before entering their unattended, unlocked car and stealing valuables.
Inspector Caroline Bakewell, of South Yorkshire Police, said: “We’ve seen a recent spike in thefts from vehicles which show no signs of entry, where the driver clearly recalls locking their doors and are confident they can be attributed to thieves blocking their signals remotely.
"Drivers are pressing their key fob and walking away from their vehicle thinking they’ve locked it, but they are having their frequency blocked by thieves.
“The only sure way to know your car is locked is to check it manually. If your indicator lights flash, wing mirrors fold in, or the horn beeps when you lock it, this is a sure sign your vehicle has locked, but the failsafe method is to give your door handle a little tug before you walk away.”
Basic jamming devices can have a range of 75 metres and affect a whole car park at the time of activation.
Inspector Bakewell added: “We have received 26 reports of thefts of this nature in the Rotherham district since February and are eager to bring this issue and the associated crime prevention advice to the attention of motorists, to enable them to protect their property.
"Please circulate this message to your friends on social media, so they can protect their vehicles.”
The issue of key jamming affects forces nationally and has previously been highlighted by the National Police Chiefs’ Council.
Two men, aged 22 and 24, from Sheffield, were arrested on suspicion of theft from a motor vehicle at Woodall Services on the M1 in January.
Both men are currently released under investigation.