A US Airways plane with 157 passengers was evacuated during a stop in Philadelphia after a threatening note was received, but a search of the aircraft turned up no explosives, authorities have said.

US Airways Flight 968 had arrived from Glasgow, Scotland and was preparing to depart Philadelphia International Airport for Anchorage, Alaska when the Transportation Security Administration ordered that it be evacuated.

Nothing explosive was found inside, FBI Special Agent J.J. Klaver told AFP.

He said the threatening letter was received in London and provided to the FBI by Scotland Yard. The investigation is now closed.

The TSA said earlier it had decided to deplane passengers and have law enforcement sweep the aircraft out of an abundance of caution after receiving a threatening note.

We received a call from the TSA and after discussion, we evacuated the flight, US Airways spokeswoman Valerie Wunder said.

About 30.8 million passengers passed through Philadelphia International Airport last year. About 30 airlines offer an average of 587 flights to 120 cities each day out of the airport, including 36 international destinations.