Port Authority spokesman Justice Karp says the closing at the airport near New York City is a precaution.
American Airlines spokesman Tim Smith tells The Associated Press the package was found behind the ticket counter at a security checkpoint where checked bags are screened.
The terminal is where American Airlines' flights are based at Newark.
TV footage shows a large number of emergency vehicles outside the terminal.
(Published 20 December 2010, 13:12 IST)