Police are asking the public to be vigilant after a "handful" of petrol thefts in the Whanganui East area.
"If they're driving through the area and there people hanging around cars or they see them walking up driveways or walking with a petrol can at 11 o'clock, 12 o'clock at night, call 111," Senior Sergeant Andrew McDonald said.
"We've had an increase of suspicious activity in and around the Whanganui East area, particularly around Whanganui Girls' College."
CCTV footage in the area showed two occasions - one on June 7 and one on July 6 - where a male Caucasian entered the hostel grounds and siphoned or attempted to siphon fuel out of cars.