Five people died and one person was missing after two floatplanes collided mid-air in Alaska while carrying passengers from a cruise ship's sightseeing expedition, officials said.

The two aircraft -- a Beaver floatplane and an Otter floatplane -- had been carrying 16 passengers from the Royal Princess cruise ship when they crashed near Ketchikan around 1:00 pm (2100 GMT), Princess Cruises said in a statement circulated by US media.

The dead included four passengers and a pilot, according to Princess Cruises. Ten people were rescued and were receiving medical care.

The US Coast Guard said three people were confirmed dead and that it was searching for three others near George Inlet, along with help from partner agencies -- including the US Forest Service and Alaska state troopers -- and good Samaritans.

Helicopters and boats were deployed by the Coast Guard for the search-and-rescue operation.

"In a remote area such as this, given our limited resources, we rely on our partner agencies and appreciate the support that good Samaritans have rendered to this point," said Captain Stephen White, Coast Guard Sector Juneau commander. 

"With the loss of life in this case, we know that the impact to Alaska is immense and our thoughts are with the community here."

The National Transportation Safety Board said it was launching a "Go Team" to investigate the cause of the accident.