PORTLAND — Portland police are investigating an armed robbery tonight in which a store clerk was told to lie on the floor of the store while the robber fled with an undetermined amount of cash.

Lt. Robert Ridge said a white male, who was wearing a ski mask and dark jacket, entered the Cumberland Farms store at 49 Pine St. around 10:30 p.m.

The suspect showed a gun and demanded money before ordering the clerk to lie on the floor. No shots were fired and no injuries were reported.

The robber is about 5 feet 9 inches tall and has a stocky build, police said.