Allentown Police are investigating an armed robbery at a gas station Sunday night.

Police said a man armed with a knife went into the US Petro gas station at 1510 W. Tilghman St. around 8:50 p.m.

He took an undetermined amount of cash from an employee and got away, police said.

The robber is described as wearing a black mask, dark hoodie and dark pants.

There were no injuries.