JUNEAU, ALASKA -- A sightseeing plane crashed Thursday in southeast Alaska, killing all six people on board, the U.S. Coast Guard said.

The plane's emergency alert beacon was activated around 11:20 a.m. when the plane crashed in the area of Misty Fjords National Monument, near Ketchikan, the Coast Guard and Federal Aviation Administration said. A helicopter company reported seeing wreckage on a ridgeline in the search area, and Coast Guard crew members found the wreckage around 2:40 p.m. A Coast Guard helicopter lowered two rescue swimmers to the site, and they reported no survivors, the agency said.

The identities of those killed in the crash were not immediately released. The Alaska State Troopers and volunteers from the Ketchikan Volunteer Rescue Squad will coordinate recovery efforts Thursday and Friday.

The plane involved Thursday, a de Havilland Beaver, was owned by Southeast Aviation LLC.

"Our hearts are shattered at the loss of six people today. We are thinking of and grieving with the families of the five passengers and our dear friend and pilot aboard the aircraft," the company said in a statement. "We are cooperating with the first responders and agencies involved, including the U.S. Coast Guard, National Transportation Safety Board and Alaska State Troopers."

The five passengers on the flight were from the Holland America Line cruise ship Nieuw Amsterdam, the company said in a statement. The ship stopped in Ketchikan on Thursday and delayed its afternoon departure after the plane crash. The company said it was making counseling services available to guests and crew.

"The float plane excursion was offered by an independent tour operator and not sold by Holland America Line," the statement said.

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

Popular among them are small plane flights to Misty Fjords National Monument, where visitors can see glacier valleys, snow-capped peaks and lakes in the wilderness area.

In 2019, two sightseeing planes collided in midair, killing six of the 16 people on board the two planes.

Southeast Aviation on its website says it provides sightseeing tours to Misty Fjords National Monument and bear-viewing sites, along with air charters to other communities in southeast Alaska.

The Coast Guard was told by the plane's operator that five passengers and a pilot were on board, Wadlow said.

Wadlow did not have details on when the plane took off. Weather conditions were a cloud ceiling of 900 feet (274.32 metres) with mist and light rain. Visibility was 2 miles (3.22 kilometres) and winds were 8 mph (12.87 km/h), the Coast Guard said.

The National Transportation Safety Board is sending a crew to investigate the crash. The team is expected to arrive in Alaska on Friday.

The FAA is also investigating.

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Thiessen reported from Anchorage, Alaska.