A police force is urging drivers to be “vigilant” following a spate of incidents where thieves stole valuables from vehicles.

Hertfordshire Constabulary says there have been 33 reported cases of vehicle crime in Hertsmere in just the first two weeks of September.

Of those, 22 had been thefts from vehicles, five of which were from vans.

The force said that attempts were also made to break into seven vehicles and a further four were stolen.

Most offences are taking place overnight, police said, with items such as bags, laptops, cash and wallets being stolen from cars and tools stolen from vans. A number of catalytic converters have also been stolen from underneath cars.

The majority of incidents have taken place in Potters Bar, although offences have also been reported in Borehamwood, Radlett and South Mimms.

Most thefts from vehicles in Bushey and Radlett have targeted insecure vehicles, police said.

Police are now urging drivers to remove any valuables from their vehicles, as well as tools from vans when they are not using them.

Detective Inspector Michael Macbeth, from the Local Crime Unit at Borehamwood police station, said: “We are thoroughly investigating these incidents and are following a number of lines of enquiry. Additional police patrols have been put in place to prevent further thefts and catch those responsible.

“Whilst these investigations continue, I would urge anyone who carries valuables or tools in their vehicles to remove them overnight or when they are not in use.

“I’d also ask people to be aware that this crime is occurring and to be vigilant. Contact police if you see anyone acting suspiciously around vehicles in your area.”

Police have offered the following tips to help you protect your vehicle and the property within it:

1. It might sound obvious, but make sure you lock the doors and shut the windows and sunroof whenever you leave your vehicle unattended.

2. Always take the keys out of the ignition even if you’re just stopping to buy a newspaper, paying for fuel, or popping back into your home to get something.

3. Be aware of your keys. Don’t leave them lying around, visible or in pockets in changing rooms where they could be taken. Don’t leave them visible on a window sill in your home or near to the front door, where they could be “hooked” through the letterbox.

4. Never leave any valuables in your vehicle - not even in the glove-box or boot - and keep ALL other possessions out of sight. Even if you know that there is nothing valuable in your coat pocket or bag left on the back seat, a thief may try their luck.

5. Remove your sat nav and its holder, and wipe away any suction marks as these could suggest to a potential thief that a sat nav is stored in your vehicle.

6. Never leave vehicle documents in your car - don’t make it easy for a thief to sell your car or provide a cover story if stopped by the police.

7. Use an approved steering lock or gear clamp, and remember to set your immobiliser and alarm if you have them.

8. Consider buying locking screws kits to secure number plates which are targeted by criminals.

9. Register your stereo, laptop, sat nav and any other property on the free online property database New windowwww.immobilise.com. It only takes a few minutes and could help police trace your property if it’s lost or stolen.

10. If you advertise your vehicle for sale on an online web site, ensure that its number plates are covered over when photographed to avoid cloning of its identity.