Investigators say the man showed an employee a black folder that contained what appeared to be a bomb. It had two or more cylinders that looked like dynamite or flares, wires and a battery-like part.
The man demanded cash and left, leaving behind the device. It did not explode and authorities were not certain whether it contained explosive material.
The suspect was described as a man in his 40s, about 5 feet 5 inches tall, weighing 190 pounds and wearing a green sweatshirt.
City News Service contributed to this report.