Battered by high winds, scaffolding at two construction sites in San Francisco collapsed Sunday afternoon — in one case, closing several blocks of Market Street near the Civic Center plaza.

In the first collapse, scaffolding materials fell about 2 p.m. from the top of a seven-story building on Seventh Street between Market and McAllister streets. Concerned more of it could fall, San Francisco police officers closed surrounding streets to pedestrians and vehicles.