St Albans and "it's surrounding localities" has seen 49 thefts of items from motor vehicles in the past two months.
According to Hertfordshire police, the crimes were committed in April and May, with many offenders described as "opportunists".
Officers believe that offenders have targeted vehicles that have been left unlocked and insecure by their owners.
READ MORE
- Harpenden: Man guilty of kidnapping and assaulting teenagers
- PICTURED: Stolen vehicles recovered in Dacorum
As a result, Hertfordshire Constabulary tried the doors of 164 car doors in the city's Clarence area earlier this week.
Six of these doors were found to be unlocked.
According to police, "The owners were immediately notified and issued some crime prevention advice".
Get more stories like this delivered to your inbox every week by signing up to our newsletter.
A spokesperson for Hertfordshire police added: "We urge motorists to lock and secure your vehicles, regardless of where you park your vehicle.
"Remove all valuables from the vehicle and leave the glove box open to deter any opportunists."
Further information can be found on the Hertfordshire police website: www.herts.police.uk
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here