Motorists were today warned to keep car keys out of sight in their homes following a spate of burglaries in which vehicles were the sole target.

Detectives are concerned that car-related break-ins may be on the rise again despite a successful purge on offenders last year.

After noting three incidents over the last four days in Bradford's Eccleshill division, officers urged home owners to be vigilant.

In November last year, the Telegraph & Argus revealed there had been 43 high performance cars stolen over the previous three months.

Following the launch of Operation Hanoi, which targeted the organised gangs, this figure was halved over the following three months.

But Detective Inspector George Marshall, of Eccleshill CID, said there have been three offences since Friday night in which a Vauxhall Vectra, Toyota Avensis and Volkswagen Golf had been taken.

He said 'lesser' criminals may have copied the actions of organised car-stealing gangs, grabbing keys to take vehicles parked in drives.

Improving car security devices meant their traditional techniques were often ineffective, leaving the only way to steal them by using the keys.

"If they see them on a kitchen table top or somewhere else in view they may try to hook them with a device through a letterbox, or smash a window," said Det Insp Marshall. An unsecured door or window provided them with an ideal opportunity, he added.

"These people are going into properties solely to steal car keys. Nothing else is being taken. If they do not see keys there, they will go elsewhere."

Drivers can minimise the risk simply by keeping them out of sight.

The rise of such thefts over recent years had created a market for thieves to supply, with people paying from hundreds to several thousands of pounds for stolen cars, said Det Insp Marshall.

"Some of them will change the number plates and drive them as their own vehicle. If they are stopped, they claim to have bought it innocently," he added.

Anyone with information on the latest stolen cars - a green Toyota Avensis (registration R108 HUG), a silver Volkswagen Golf (registration J7 DUT) and a silver Vauxhall Vectra (registration R956 DJX) - should contact Eccleshill police on (01274) 376059.