PHILADELPHIA (AP) - Production has been shut down at Boeing's helicopter plant in suburban Philadelphia.

Pennsylvania congressman Joe Sestak says he's been told by a Boeing executive that a plastic cap was found in the fuel line of a V-22 Osprey fuselage. He says Boeing could not rule it out as a willful act, so it stopped production on its lines and notified defense officials.

Sestak's district encompasses the plant in Delaware County.

The company says in a statement that debris was discovered during quality inspection of an aircraft in production and the incident is under review.

A disgruntled ex-Boeing worker admitted in court recently that in May he used his work-issued wire cutters to sever about 70 electrical wires running together from the cockpit to the main body of an H-47 Chinook. That also prompted the company to shut down production lines.