Human error caused a cruise ship to abruptly tilt at sea last week, sending furniture and debris flying about the boat and injuring 240 passengers, a cruise line official said.

Though federal investigations continue, Princess Cruises president Alan Buckelow wrote in a letter to passengers that "the incident was due to human error and the appropriate personnel changes have been made."

No further specifics were given in the letter, which was dated Monday and posted on the company's Web site.

Company spokeswoman Julie Benson said in a telephone interview Tuesday that some crew members had been reassigned, but she declined to give further details.

"The captain remains in command of the ship. We have the utmost confidence in him," she said. "It was an isolated situation and I think passengers generally understand that."

The Crown Princess unexpectedly heeled to its side last week shortly after departing Port Canaveral, where it had stopped before a scheduled return to New York to complete a nine-day Caribbean cruise.

The ship, carrying 3,100 passengers and 1,200 crew, tilted an estimated 16 to 18 degrees, tumbling passengers, chairs, tables and other objects, and seriously injuring at least 20 people.

Those aboard described a terrifying interlude in which they were certain the entire 113,000-ton ship would tip over, and customers received a full refund for the journey.

More than 90 people were taken to hospitals, two with critical wounds. As of Monday all but one had been released.

The ship returned immediately after the incident to Port Canaveral, on Florida's east coast, but departed again for New York two days later and picked up a new load of passengers for a similar, shortened cruise.

"We express our sincerest apologies for this regrettable event, and fully understand that this was a distressing experience for all who were on board," Buckelow wrote in the letter.

A Coast Guard spokesman declined to comment on the cruise line's statement except to say the agency's joint investigation with the National Transportation Safety Board wasn't yet complete.

At the time of the incident, seas were calm. The ship was on autopilot, with its captain, Andrew Proctor, away from the bridge. The company earlier said Proctor has worked for them nearly 35 years and had an "exemplary record."

Princess is one of 12 brands operated by Miami-based Carnival Corp., the world's largest cruise operator. The Crown Princess was christened just last month before embarking on its maiden voyage to the Caribbean from its home terminal in New York's Brooklyn borough.

A similar tilt occurred in February on a ship also operated by Princess. Soon after leaving the Port of Galveston, the 2,600-passenger Grand Princess made an emergency turnaround because a passenger suffered a heart attack. The ship tipped sharply to its side, injuring 37.

The cause of that incident, too, was determined to be human error.