At least four people are dead after two float planes collided in mid-air off the Alaskan coast on Monday, according to the U.S. Coast Guard.
Two other people are missing, the U.S. Coast Guard reported, adding that 10 people were rescued and are receiving medical care.
Both planes were carrying cruise passengers from the Royal Princess cruise ship who were taking aerial tours around 1 p.m., said Princess Cruises in a statement.
WATCH: Float plane collision in Alaska leaves at least 4 dead, 10 in hospital
The U.S. Federal Aviation Administration (FAA) said the crash occurred in Coon Cove near George’s Inlet, involving a de Havilland DHC-2 Beaver and a de Havilland Otter DC-3.
According to the FAA, the aircraft “collided in mid-air under unknown circumstances.”
The Beaver had five people aboard, and the Otter had 11 people aboard, the FAA said.
The FAA said neither aircraft was under air traffic control during the crash. It is investigating along with the National Transportation Safety Board.
WATCH: Float plane crashes into remote lake north of Pemberton
Princess Cruises says the flight was operated by Taquan Air and was on a shore excursion booked through the cruise line.
The U.S. Coast Guard has only confirmed four fatalities, three from the Beaver and one from the Otter. On Monday night, it said it was still searching for two people from the Beaver.
However, Princess Cruises said four cruise ship passengers and the pilot on the smaller aircraft, which was operated by an independent tour company, died.
The U.S. Coast Guard said it was responding with a cutter, a MH-60 Jayhawk helicopter and two 45-foot response boat mediums and that it was flying in relief crews.
“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 Coast Guard Capt. Stephen White, Coast Guard Sector Juneau commander in a statement.
“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.”
Taquan Air says it has suspended all flights and is co-operating with investigators.
“We are devastated by this news, and our hearts go out to our passengers and their families. At this time, we are in the midst of an active crisis response, and our focus is on assisting these passengers, the pilot, our staff, their families and loved ones and first responders,” said the company in a statement.
Princess Cruises says it has activated its Care Team to offer help to the passengers involved.
“We are incredibly distressed by this situation, and our thoughts and prayers are with those onboard the planes and their families. Princess Cruises is extending its full support to travelling companions of the guests involved,” said the company.
Cruise passenger Terry O’Neill said people on the boat were being offered access to grief counsellors.
“(The captain) said if any passenger wants to cancel any excursion over the duration of the trip, they will receive a full refund,” he added.
WATCH: Pilot uninjured after crashing his small float plane during take-off (Aug. 2018)
The Royal Princess departed Vancouver last Saturday and was scheduled to arrive in Anchorage, Alaska, on Saturday, May 18.
Weather conditions included high overcast skies with nine mile-per-hour (14 kilometre-per-hour) southeast winds.
—With files from the Associated Press