Thieves stole fuel from a car in Broughton, north of Drumelzier, after drilling a hole in its petrol tank.
The theft was carried out between Friday, August 26, and last Thursday.
The car targeted was a silver Mercedes C Class parked on the forecourt at Scott Vehicle Repairs in Galavale.
Police and community support officer Niki Craig, of Peebles police station, said: “As well as being a criminal act, the action taken to steal the fuel was extremely dangerous to the culprit and other members of the public.
“The fuel could have ignited at any time, causing serious injury or worse.”
Three similar incidents were reported in June at Hartree, Carlopps and Broughton Village Hall.
Inquiries are ongoing, and extra police patrols will be taking place in and around Broughton.
Any witnesses are asked to call Police Scotland on 101 or Crimestoppers on 0800 555111.