A shark that was seen circling kayakers has led lifeguards to close a San Diego County beach.

A 1 1/2-mile stretch of beach from La Jolla Cove to Scripps Pier was closed Saturday afternoon after a confirmed sighting of the 8- to 10-foot hammerhead shark.

San Diego Fire-Rescue spokesman Lee Swanson said the shark appeared to be acting aggressively toward a group of kayakers and followed them into shore.

Lifeguards reviewed a video taken by a kayaker of the shark and ordered the beach closed. A marine biologist at the nearby Scripps Institution of Oceanography confirmed that the size, species and behavior of the shark warranted the closure.

Swanson said there have been no additional sightings. Lifeguards will reassess the water Sunday morning to decide whether to reopen the beach.