BOSTON -- Beach areas in Chatham were closed by the harbormaster Friday afternoon after planes spotted three to four more sharks in the waters off the coast.

A plane surveying the waters off South Beach and Monomoy Island detected the sharks in an area east of South Beach where a shark was successfully tagged on July 27, officials there said.

Sharks were located and tagged in the same area last year.

As a result, the harbormaster has closed the area to swimmers along a portion of the eastern shoreline of South Beach for an indefinite period of time.

Other portions of the shoreline remained open to swimmers, except within 300 feet of gray seals.

Swimmers and boaters were advised to get out of the water if a shark is spotted and asked to contact authorities.