Security was downgraded to the "heightened" state of alert, the same state of readiness the bridge has been operating under since the Sept. 11 attacks, said Mary Currie, spokeswoman for the Golden Gate Bridge Highway & Transportation District. National Guardsmen patrolled below the bridge and federal officials watched the skies.
The California Highway Patrol, FBI, Coast Guard, Federal Aviation Administration and other agencies "all aggressively are doing exactly what needs to be done to protect and keep the Golden Gate Bridge secure," Currie said.
Traffic for Monday morning's commute appeared normal.
The bridge was placed on a "super-heightened" state of alert Friday through Sunday after information was shared through an interagency coalition Friday, Currie said.
She would not elaborate on the details of the threat or specify the information's source. However, the Contra Costa Times reported that the bridge district board's president, Harold C. Brown, said the FBI was gauging the credibility of a threat that terrorists planned to crash an aircraft into the span.
There also had been a "super-heightened" alert in July, when Spanish authorities recovered a videotape of potential U.S. targets believed to have been filmed by members of the al Qaeda terrorist network.
The footage, filmed before the Sept. 11 attacks, included shots of the bridge's suspension anchors and also featured other American landmarks, including Disneyland, Chicago's Sears Tower and New York's Statue of Liberty.