Two seaplanes collided in mid-air on Monday over southeastern Alaska, killing at least four of those aboard, injuring 10 others and leaving two people missing.

A team of federal accident investigators was expected to arrive in Alaska on Tuesday to try to piece together what caused the crash.

The two aircraft – one with 11 passengers and crew, the other with five people aboard – went down over water about 25 to 30 miles northeast of Ketchikan, according to Coast Guard Petty Officer Jon-Paul Rios, speaking from Juneau.

The passengers were from the cruise ship Royal Princess and were on sightseeing flights.

The crash site, which the FAA said was at Coon Cove near George Inlet, lies in the vicinity of a popular tourist lodge that runs excursions to the nearby Misty Fjords National Monument, about 300 miles south of Juneau, Alaska’s capital.

One of the aircraft involved was a de Havilland DHC-2 Beaver with five people aboard, and the other was a de Havilland Otter DHC-3 carrying 11 people, FAA spokesman Allen Kenitzer said.

The Ketchikan-based operator of the larger plane, Taquan Air, said its pilot and nine passengers were rescued and receiving medical attention, but one passenger’s fate remained unknown.

Alaska plane crash – Coon Cove

That group was returning from a flight-seeing tour of Misty Fjords when the crash occurred, Taquan said in a statement.

Mr Rios initially reported 10 people from the two planes were receiving medical care, with six others listed as unaccounted for. He later said four of the missing had been confirmed as dead.

Local emergency responders worked with state and federal agencies and good Samaritan vessels to help rescue and recover victims.

"It’s been a long day and the crews have been working really hard to rescue people and recover the deceased," Deanna Thomas, a spokeswoman for the Ketchikan Gateway Borough, the local government, said on Monday evening.

A spokeswoman for Taquan Air said the company had suspended operations while federal authorities investigate the deadly crash.

"We are devastated by today’s incident and our hearts go out to our passengers and their families," Taquan said.

Cindy Cicchetti, a passenger on the Royal Princess cruise ship told the AP that the ship captain announced that two planes were in an accident on Monday. She said the ship was not leaving as scheduled and there weren’t any details as to how the accident will affect the rest of the trip.

The ship left Vancouver, British Columbia, on May 11 and is scheduled to arrive in Anchorage on Saturday.

"Our thoughts and prayers are with those who lost their lives and the families of those impacted by today’s accident. Princess Cruises is extending its full support to traveling companions of the guests involved," Princess Cruises said in a statement.

Neither of the single-engine planes was under air traffic control when they collided, and circumstances of the crash were not immediately known, Mr Kenitzer said.

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