Police are investigating the robbery of a supermarket at Bonnyrigg in Sydney’s south-west last night.

About 9:15pm, Thursday 25 July 2013, a man forced his way into the office of the supermarket on Bonnyrigg Avenue via the roof of the building.

Once inside the office he threatened a female staff member demanding cash.

The man was handed a large amount of cash before the woman was able to run for help and alert her colleagues about the robbery.

The man, who was wearing a balaclava, was chased by staff and was last seen running north along Pomo Close, Greenfield Park.

No one was injured in the robbery and police were contacted and attended the scene.

A search of the area was conducted with the assistance of the Dog Unit however the man was not located.

Police from Fairfield Local Area Command are investigating the robbery and are looking for a man who has been described as wearing a black balaclava, a green hooded jumper with a white motif on the front, blue jeans and brown boots.