A sight-seeing plane has crashed in south-east Alaska, killing all six people on board, the US Coast Guard says.

The plane’s emergency alert beacon was activated late on Thursday morning (local time) when the aircraft crashed in the area of Misty Fjords National Monument, near Ketchikan, the Coast Guard and Federal Aviation Administration say.

A helicopter company reported seeing wreckage on a ridgeline in the search area, and Coast Guard crew members found the wreckage in the afternoon.

A Coast Guard helicopter lowered two rescue swimmers to the site, and they reported no survivors, the agency said.

The five passengers on the flight were from the Holland America Line cruise ship Nieuw Amsterdam, the company said.

The ship stopped in Ketchikan on Thursday and delayed its afternoon departure after the plane crash.

Ketchikan is a popular stop for cruise ships visiting Alaska, and cruise ship passengers can take various sightseeing excursions while in port.