"There are two people that we're still searching for at this time," Coast Guard Petty Officer Jon-Paul Rios told ABC News in an interview airing Tuesday on "Good Morning America."
"Our crews are out there searching diligently alongside our partner agencies and some good Samaritans," he added. "They've been searching throughout the day, by both air and by sea."
The deadly collision took place Monday afternoon in Coon Cove, Alaska, according to the Federal Aviation Administration. A de Havilland DHC-2 Beaver with five people on board and a de-Havilland Otter DHC-3 carrying 11 people clashed in midair "under unknown circumstances," the FAA said in a statement Monday.
Ten people with injuries from the incident were taken to PeaceHealth Ketchikan Medical Center, according to hospital spokeswoman Mischa Chernick. Three of the patients are listed in serious condition, while seven are in fair condition, Chernick told ABC News.
Both planes were on sightseeing tours, carrying guests from the Royal Princess cruise ship, which is on a seven-day voyage that departed Vancouver on May 11 and is scheduled to arrive in Anchorage on Saturday, according to Princess Cruise Lines.
The aircraft collided approximately eight nautical miles from Ketchikan, Alaska.
The two people still missing in the incident -- one Australian and one Canadian -- were both guests on the Royal Princess cruise ship, which has since departed the area and continued on its voyage, according to Princess Cruise Lines.
"All of us at Princess Cruises are deeply saddened by this tragic news and we are extending our full support to the investigating authorities as well as the traveling companions of the guests involved," Brian O'Connor, a spokesman for the cruise line, said in a statement Tuesday. "We immediately activated our Princess Care Team employees in the region and sent additional team members to Ketchikan overnight to assist the families impacted."
One of the planes was operated by Taquan Air, which said it has suspended all scheduled flights and is cooperating fully with investigators.
"We are devastated by this news and our hearts go out to our passengers and their families," the airline said in a statement Monday.
The Coast Guard, the FAA and the National Transportation Safety Board are all investigating the incident.