Philadelphia police are warning residents to be wary of strangers knocking at the door in the wake of a robbery of a Southwest Philadelphia man by a woman posing as a postal worker.

About 1 p.m., the woman, holding what looked like a package, came to the door and asked the man his name.

As he signed for the package, the woman pulled out a handgun, stuck it in his face and ordered him inside. She then signaled to three men who emerged nearby and they entered the house, police said.

The intruders tied up the man, whom police have not identified. A woman who was upstairs when the intruders entered the home, which is on Grays Avenue near 61st Street, was bound with duct tape.

The robbers then tore through the home, stealing a coin collection, electronics and $700 in cash and fled out the back door, said Lt. John Walker, of Southwest Detectives. The man and woman were not injured. News reports placed the value of the collection at $10,000.

The Postal Service said that the woman was not an employee. *

- Staff and wire reports