Nine heavy duty batteries were stolen from plant machinery parked up for the night on Monday, april 21.
Theives struck some time between 10am and midnight on Easter Monday, targetting vehicles parked next to Lake House, just off the B4031 at Croughton.
In the course of the theft the vehicles were substantially damaged and 500 litres of red diesel was siphoned off.
Northants Police would like to hear from anybody who may have seen suspicious activity at the main gate to Lake House, which is where the offenders are believed to have entered the site.
Witnesses to this incident, or anyone with information, should call Northamptonshire Police on 101 - alternatively, information can be given anonymously to Crimestoppers on 0800 555 111.