WASHINGTON (Reuters) - Authorities found a suspicious object at Dulles International Airport near Washington on Saturday, prompting the closure of several gates on the eve of the 10th anniversary of the September 11 attacks.

Airport spokesman Rob Yingling said the airport was operating normally after some planes were reassigned to other gates for arrival and departure.

The suspicious object was found in a freight container at about 4:30 p.m. and four hours later was still being checked by Virginia state police near one of the airport concourses.

Dulles is about 22 miles west of Washington, where authorities are on alert ahead of the 10th anniversary of the al Qaeda attacks on the Pentagon and the World Trade Center in New York using hijacked passenger planes.

(Writing by Bill Trott; Editing by John O'Callaghan)