UPDATE: The rig has been secured, reports CBS SF. All has returned to normal.

A precariously teetering window-washer's scaffold atop Embarcadero 1 (301 Clay) in San Francisco has prompted a 29th floor evacuation, street closures, and Muni rerouting. (How almost sort of First Wives Club!)

Here's what we know: no injuries have been reported so far, no person is trapped on the scaffold, Battery Street remains closed from Clay to Sacramento, and traffic in the area has been rerouted.

A couple images of the scene: