COPENHAGEN, Denmark — Norwegian officials said Monday they have opened an investigation into why a cruise ship carrying more than 1,300 people set sail despite storm warnings, forcing a major evacuation.

Hospital officials have said one person is in critical condition, and eight others are still hospitalized after the Viking Sky got into trouble off the Norwegian coast on Saturday. Authorities launched a daring rescue operation, taking 479 passengers off the ship by helicopter.

Dag S. Liseth of Norway's Accident Investigations Board said "the high risk which the ship, its passengers and crew were exposed to made us decide to investigate the incident."

The ship, which had left the northern city of Tromsoe and was headed for Stavanger in southern Norway, suffered engine trouble before the mayday call and was drifting toward the rocky coast. Many shipwrecks have occurred in the area through the years.

The airlift evacuation went all through Saturday night and into Sunday morning, slowing for a bit when two of the five rescue helicopters had to be diverted to save nine crewmembers from a nearby ailing cargo ship.

The Viking Sky is now docked in the port city of Molde, 241 miles northwest of Oslo, which it eventually managed to reach on its own engines.

Liseth said investigators were headed to Molde Monday and declined to speculate as to why the Viking Sky captain had decided to sail despite the weather warning. He couldn't immediately say how long the ship would remain in Molde.

Yngve Skovly of the police in Moere and Romsdal district where Molde sits, says that there is no suspicion of a criminal offense but police have opened an investigation to find out why the ship had engine problems. That probe would be part of the one by the Accident Investigations Board.

The Viking Sky is a relatively new ship, delivered in 2017 to operator Viking Ocean Cruises.

The ship was on a 12-day cruise along Norway's coast before its scheduled arrival Tuesday in the British port of Tilbury, on the River Thames. The passengers were mostly an English-speaking mix of American, British, Canadian, New Zealand and Australian citizens.

The U.S. Embassy Oslo said in a statement Sunday that more than 600 Americans were on the cruise, and thanked those who helped get U.S. citizens off the ship.

“Now that the Viking Sky has arrived safely in Molde, I want to take a moment to express my deepest appreciation and gratitude to those who have been working tirelessly for more than 24 hours to ensure the safety and security of all passengers on board the cruise ship," U.S. Ambassador to Norway Kenneth J. Braithwaite said in a message posted on Facebook.

"Thank you to everyone for supporting our U.S. citizens in distress, whose safety and security remain—as always with the Department of State in all that we do abroad—our highest priority.”

All passengers were expected to be flown out on Norway by Monday evening, police said.

On Sunday, the operator said the ship's next scheduled trip, to Scandinavia and Germany, that was to leave on Wednesday, was canceled.

Calls to Viking Ocean Cruises on Monday were not immediately returned.