At about 1 p.m., someone saw a man placing a package into a news rack at the intersection of Post and Kearny streets, San Francisco police spokesman Sgt. Wilfred Williams said.
The witness approached some firefighters who were in the area on an unrelated call, and the firefighters contacted police, Williams said.
The Police Department's bomb squad was dispatched to the scene and streets in the area were shut down. Several Muni lines were disrupted by the closure.
Shortly after 2 p.m., police determined the package was harmless and the area was reopened to traffic. Williams said the item placed in the news rack was a shopping bag. It contained some items but none that posed a threat, he said.
The incident occurred just hours after a bomb scare at the State Building at 350 McAllister St., where a suitcase left near an elevator in an underground garage prompted a bomb squad response and a street closure. The suitcase turned out to be empty.