A worker was forced to hand over hundreds of pounds of takings after a robber banged on a fire door, tricking him into opening it.
The employee, a 31-year-old from Leyland, was closing up at the Subway sandwich store on Liverpool Old Road, Penwortham, near Preston, at around 10.50pm on Tuesday when he heard a noise at the rear door.
Police say the shop had previously suffered nuisance from young people at the back of the building.
The worker opened the door to see what had happened, and was faced by the robber. He had his hand in a black binbag, as if he was hiding a weapon.
He threatened the worker and the victim told officers he was made to open the store’s safe and hand over takings.
Det Sgt John Crichton, of Preston CID, said: “This is an unusual crime for the Penwortham area. We would ask other shop owners in the area to be vigilant.”
Witnesses can call 101.