Authorities said six people were left dead following a crash of a sightseeing floatplane in southeast Alaska on Thursday.

Onboard the de Havilland Beaver were cruise ship passengers, who, according to the U.S. Coast Guard did not survive the crash in the Misty Fjords area.

At around 11:20 a.m., an emergency beacon was activated. The wreckage was found by a search helicopter at 2:37 p.m. on a ridgeline.

“Our thoughts and prayers are with the family and friends of the victims and with our guests and team members who are affected by this tragedy,” cruise line Holland America expressed through a statement.

The cruise company clarified that the excursion was not put on sale by Holland America cruise line.

It used an aircraft owned by a private company, Southeast Aviation.

The company said the people on board the plane were from Nieuw Amsterdam. They are close to a week’s cruise that departed on Saturday from Seattle, according to a report by NBC News.

According to the Alaska State Troopers, the crash site was in a “steep mountainous area”. The aerial search efforts are made difficult by poor visibility and worsening weather. It said that efforts are being done to retrieve the victims.