SAN FRANCISCO — Authorities temporarily shut down the San Francisco-Oakland Bay Bridge after a suspicious device was found, snarling traffic on both sides of the crossing on a busy Friday afternoon.

Authorities were notified around 1 p.m. about the device on the Treasure Island on-ramp, California Highway Patrol Officer Sam Morgan said. The island is midway across the span.

Morgan said officials decided to close lanes and cleared all vehicles from the bridge nearly an hour later.

Authorities reopened the westbound lanes, then the eastbound side, around 3:30 p.m. when San Francisco police neutralized the threat.

No further details on the device were released. Television news reports showed a bomb squad robot removing what appeared to be a small cylindrical object from the ground.

The closure caused a ripple effect on roadways into and out of San Francisco.

Traffic is typically heavy on Fridays, but it was exacerbated by several stadium events in the region. Thousands of drivers headed to San Francisco Giants and Oakland A's home games, a Jay-Z and Justin Timberlake concert at Candlestick Park and other concert venues headlined by John Mayer and the indie-rock band the Postal Service.

The bridge carries about 280,000 vehicles a day between San Francisco and heavily populated cities to its east.