Thieves have been siphoning off fuel from HGVs parked in lay-bys along the A14.
The spate has led to a warning from police, urging people to be on their guard against fuel theft.
A police spokesman said there had been a number of incidents in the last month where diesel had been siphoned from HGVs while parked overnight.
Most of the incidents have happened in lay-bys between Catthorpe and Thrapston and one on the Westbound carriageway at Rothwell.
Police would like to hear from anybody who has seen anything suspicious around these lay-bys during the past few weeks by calling 101.