MADRID (AP) — Spain has prohibited yachting across 100 kilometers (62 miles) of its northwestern coast after a number of sailboats have been damaged by orca whales knocking their hulls.

Spain’s transport ministry issued the week-long prohibition for the vessels under 15 meters (49 feet) long starting on Tuesday night. It said the area covered by the ban could be extended to “follow the migration routes” of the whales.

Boats are allowed to leave port to go into the open sea between the capes of the Prioriño Grande and la Punta de Estaca de Bares, but they must not remain near the coast off the country's northwestern tip.

The ministry says the first reported incident occurred on Aug. 19. Since then, it said an unspecified number of sailboats have been damaged by orcas, with some needing assistance from Spain’s maritime rescue service after their rudders were wrecked.

Spanish television has shown footage taken by sailors of groups of orcas swimming extremely close to their boats.

No injuries have been reported so far.