Police said a woman - believed to be between 25 and 30 years of age - walked into the Subway restaurant yesterday at 11.15am, demanding money and "waving a knife".
"She was waving a knife and threw a bag over the counter, asking the attendant to fill it with money,"Acting Sergeant Andrew Caruana said.
Police said the woman then removed her top, exposing a black bikini top, before running to a waiting getaway car. She was last seen driving off on Vanderlin Drive in a maroon Mitsubishi Magna.
Yesterday afternoon, staff at the Subway restaurant were not able to say how much money was missing, as they had to wait for the day's tally, but it is believed the woman stole more than $500.
She is described as Caucasian with dark hair, below shoulder length, and was wearing a maroon top, brown shorts and thongs.