Detectives are hunting a man seen breaking into the back of a van before it was torched during the early hours.
Officers say the unknown male — believed to be in his late 20s to early 30s — walked away from the Renault box van parked in Nursery Lane, Kingsthorpe, near to the junction of Cranford Road, at around 1.30am on December 19.
A Northamptonshire Police spokesman said: "The suspect is described as a white man, around 5ft 6in and slim build. He had short hair and wore a dark jumper and jeans.
"We would like to hear from anyone with information about the incident. Please call 101 using incident number 21000737332."