This story has been updated.

Some gates at Concourse B at Dulles International Airport were shut down late Saturday afternoon after what was thought to be a suspicious item was discovered in cargo, but they were re-opened by 8:30 p.m., according to an airport spokesman.

The action came as security in the Washington region was tightened while government officials continued investigating a possible terrorist attack timed to the anniversary of Sept. 11.

The area around the container was cordoned off as authorities investigated, said Rob Yingling, a spokesman for the Metropolitan Washington Airports Authority.

He said the airport operated normally despite the gate shutdowns and the cargo investigation.

Yingling said the gates were reopened after the cargo pallet was X-rayed, and nothing harmful was found inside, the Associated Press reported.