California Highway Patrol Officer Sam Morgan says authorities were notified around 1 p.m. Friday about the device on Treasure Island, midway across the span.
He says officials decided to close the bridge an hour later. They reopened westbound, then eastbound lanes shortly after 3 p.m. when police neutralized the threat. No further details on the device were released.
The closure caused a ripple effect on roadways. Traffic typically is heavy on Fridays, but it was expected to be exacerbated by several stadium events in the region. Thousands of drivers were anticipated on the roads because of Giants and Oakland A's home games and a Jay Z and Justin Timberlake concert at Candlestick Park.