Masked men robbed a petrol station in Spaldwick before setting it alight.
The trio drove up to Spaldwick Service Station on the A14 westbound carriageway in a dark Honda 4x4 vehicle at about 3.30am on Monday (August 3).
The station was open but the entrance was locked and the men broke in using an axe.
They asked a male member of staff, who was on his own, to show them where the safe was before stealing cash from the safe, alcohol, cigarettes and a slushy machine.
They then covered the rear of the store in an unknown fluid and set it alight.
The member of staff was not injured but left shaken and upset.
A spokesman for Cambridgeshire Fire and Rescue said: “The main building was well alight and heavy smoke was issuing. The forecourt was not affected and fuel pumps were isolated.
“Twelve firefighters wearing breathing apparatus used hose reels and jets to extinguish the fire and positive pressure ventilation fans to clear smoke.”
Det Sgt Sarah Sleaford, who is investigating, said a burnt out Honda 4x4 was discovered in Corby, Northamptonshire, at about 5am the same day.
She said: “We suspect this may have been the vehicle used in the crime so I would appeal for anyone who saw this vehicle before or after the crime to contact police.
“This was a terrifying experience for the member of staff at the filling station, which was destroyed by the fire. I would urge anyone with any information, no matter how insignificant it may seem, to contact me.”
Jim White, district councillor for Ellington, posted on Twitter: “A truly shocking, senseless and appalling crime. My thoughts are with the young man on duty at the time.”
Contact Det Sgt Sleaford on 101, or Crimestoppers, anonymously, on 0800 555111.