All nine people aboard a flightseeing tour, eight of them passengers on a Holland America Line cruise ship, died Thursday in a plane crash near Ketchikan, according to the National Transportation Safety Board.

Alaska State Troopers in Ketchikan got a report at 2:06 p.m. that the float-equipped DeHavilland DHC-3 Otter was overdue. Officials tracked an emergency locator transmitter that was activated in the vicinity of Misty Fjords National Monument, said Clint Johnson, NTSB Alaska chief.

Promech Air, a Ketchikan-based charter and sightseeing service, operated the plane and said in a statement late Thursday that the cause of the crash remained under investigation.

Troopers reported that a Temsco Helicopters pilot spotted the downed plane about 800 feet above Ella Lake against a granite rock face, troopers said. Alaska State Troopers, the Coast Guard and the Ketchikan Volunteer Rescue Squad responded to the crash site.

The plane crashed in "an area of steep, mountainous terrain about 25 miles northeast of Ketchikan," NTSB said in a statement.

By 8 p.m., Johnson had confirmed that all nine people onboard the plane had died.

Troopers said search-and-rescue workers reached the crash site around 6 p.m. and confirmed the deaths of the eight passengers and pilot. Due to bad weather, they will not attempt to recover the bodies until Friday.

The identities of those killed in the crash will not be released until their relatives have been notified, troopers said.

"There is nothing I can say that can alleviate the pain and overwhelming sense of loss that we and the loved ones of those affected are feeling," Marcus Sessoms, president of Promech Air, said in a statement. "At this moment, all of us share the pain and anguish of this terrible event. Our thoughts and our prayers go out to everyone touched by this tragedy."

Holland America Line said in a statement earlier Thursday that Promech owned the plane that crashed and was operating a shore excursion sold through the cruise line.

"We are incredibly distressed by this situation, and our thoughts and prayers are with those onboard the plane and their families," the statement said. "Holland America Line is extending its full support to traveling companions of the guests involved."

The eight passengers had been aboard the Westerdam on a seven-day round-trip cruise that left Seattle on June 20, the statement said. On Thursday afternoon, the ship was docked in Ketchikan.

Promech Air said in a statement that the DeHavilland DHC-3 Otter single-engine plane that crashed was one of five Otters it operated.

"The Magnificent Misty Fjords by Floatplane" is one of several tours offered by Promech Air, according to the company's website. The cost is listed at $229 per person for about a two-hour trip, which includes a 10-minute water landing on a lake or fjord.

NTSB said it was sending a team from its Alaska regional office, led by investigator Brice Banning, to investigate the crash.

Chris John of the Ketchikan Volunteer Rescue Squad said 13 volunteers with the organization went out to search the scene of the crash Thursday in two helicopters and two floatplanes. He described conditions as "very turbulent" with winds around 25 mph.

"The conditions were really steep," John said. "It was a bad crash site."

Jerry Kiffer, president of the rescue squad, said the plane was heavily damaged in the crash. It sat upright on a 60-degree slope at the base of a cliff when the responding crews arrived.

"It's kind of hanging on the side of the mountain," Kiffer said. "The floats, of course, are broken off and it's actually (lying) on top of the floats with the tail hanging out over about a 30- or so foot drop."

Those responding to the crash, he said, will likely have to use rope to steady the plane before rescue efforts move forward.

"We'll have to do some stabilization and get the aircraft safe to get inside before we start moving the victims," he said.

The National Weather Service reported scattered rain showers from about 9 a.m. to 3 p.m. Thursday at Ketchikan International Airport, with winds between 6 mph and 17 mph. Wind gusts hit 26 mph around noon, according to the weather service.

In July 2013, a DeHavilland DHC-3 Otter crashed at the Soldotna Airport, killing all 10 people onboard. The Anchorage Daily News reported it was the worst aviation accident in Alaska in at least 25 years.