An American woman passenger died and four others were injured after a suspected “rogue wave” hit a luxury cruise ship headed back from Antarctica.

The massive wave hit the Viking Polaris cruise ship during a storm on Tuesday, November 29. In its update on Thursday, the Viking Travel Company said the ship was traveling to Ushuaia, Argentina, when the tragedy struck. Ushuaia is usually the main starting point for the long journey to Antarctica.

The statement by Viking Cruises confirmed that a passenger had died following the incident and expressed their sympathies and condolences to the family. The company also said they had already notified the family of the woman.

The ship’s medical staff and onboard doctor treated the four other passengers who got hurt and had non-life-threatening injuries. The company did not publicly identify the deceased woman.

The Viking Polaris sustained limited damage from the incident, and it docked in Ushuaia, almost 2,000 miles south of Buenos Aires, on Wednesday afternoon.

According to Argentine authorities, the deceased woman, who was 62 years old, got hit by broken glass when the wave hit the ship during a storm on Tuesday, breaking cabin windows.

Suzie Gooding, another passenger on the ship, said that passengers onboard wondered if they had hit an iceberg. She said that the rogue wave was sudden and shocking. Even though there are no icebergs in that part of the ocean, she said that’s how the wave felt when it hit the ship.

The company said its main focus was the safety and well-being of its passengers and crew. After careful consideration, they decided to cancel the next scheduled departure for the Viking Polaris, which would be December 5-17 for the Antarctic Explorer itinerary. The Viking Customer Relations office notified all guests impacted by the unfortunate incident, and the company was working on arranging return travel for everyone.

A federal court in Ushuaia has opened a case to probe the incident.

The Viking Polaris is a huge 665-foot-long ship built in 2022, with the capacity to carry over 600 people, including 378 passengers and 256 crew members.

The National Oceanic and Atmospheric Administration (NOAA) describes a rogue wave as a sizable unexpected wave that can be extremely dangerous. According to the website, scientists call rogue waves “extreme storm waves,” which are often more than twice the size of regular surrounding waves. They also hit from a different direction than the wind and already existing waves.

Once seen as a myth reported by explorers and mariners, the NOAA says that these killer waves can be very unpredictable and look very frightening, with most reports of such waves describing them as having the appearance of steep walls of water. According to the agency, these waves are rare and are still under research.

Although experts are still researching how they form, the NOAA states a few known causes for rogue waves, including constructive interference, which relates to oceanic waves, and the shifts in wave energy.