The 7-Eleven on West Central Street was robbed for the fourth time since August early Monday morning, this time at gunpoint, according to Natick Police.

A single suspect was reportedly carrying a black semi-automatic pistol when he demanded money from the cashier just after midnight. The suspect left on foot with an undetermined amount of money and was unable to be located, despite searches by several police units, including the Massachusetts State Police K-9 division, said Lt. Brian Grassey of the Natick Police Department.

The suspect is described as a 5'4" tall male with black hair, last seen wearing blue jeans, a black jacket and a black flat-rimmed hat with an unknown logo. He used a white t-shirt or towel to cover his face, Grassey said. The suspect may also have a large red mark (possibly paint) on the back of his hand.

No one was injured in the robbery, which is still under investigation.

The same 7-Eleven was robbed in October, and twice in one week in August 2011.

Anyone with any information is asked to call the Natick Police Detective Division at 508-647-9520 or fill out an online anonymous report.