A security alert was lifted after a suspicious item forced evacuation of an area around a cargo container and several gates in a concourse at Dulles International Airport, local media reported Saturday.

Two outbound flights were delayed because the aircraft were within the perimeter. However, the airport was operating normally after some aircraft moved to other gates for arrival and departure, according to the report.

The suspicious item was found at about 4:30 p.m. local time (2030 GMT), said Rob Yingling, spokesman of Metropolitan Washington Airports Authority, adding that an explosive ordinance disposal team from Virginia state was on the scene.

Four hours later, the bomb disposal team declared an all-clear, said the spokesman.

The United States is on high alert triggered by a "specific, credible but unconfirmed" terror threat surrounding the 9/11 anniversary. Dulles Airport is only about 35 km from west of Washington.

U.S. President Barack Obama called for "heightened state of vigilance and preparedness" during a meeting Friday morning with his national security team to review ongoing efforts to mitigate potential terrorist threats.

Security tightened in New York City before 9/11 anniversary