Fuel has been siphoned from lorries parked in Smalley.
The first of two incidents took place overnight between Thursday, January 14 and Friday, January 15. Fuel was believed to have been siphoned from vehicles parked in the yard at Allsop Plant and Haulage, off Heanor Road.
A similar incident also happened overnight between Thursday, January 21 and Friday, January 22.
PCSO Courtney Chetwyn of the Shipley, Smalley and Horsley Safer Neighbourhood Policing Team, said: “I would urge anyone who may have noticed anything suspicious or with information about these incidents to contact us.
“We would also advise motorists to be extra vigilant and for businesses to consider using extra security measures to help them avoid becoming a victim, such as installing lockable filler cap, parking vehicles in well-lit areas or using special diesel dye to deter thieves.”
Anyone with any information should contact Derbyshire police on 101, quoting crime number 3109/16, or call Crimestoppers anonymously on 0800 555 111.