(4:27 p.m. EST) -- U.K.-based Saga Holidays was forced to cancel its 31-night Caribbean itinerary aboard Saga Ruby, due to a faulty generator affecting the ship's air conditioning system.

The ship will continue in the Mediterranean, where it can operate normally at its current generator capacity.

According to a Saga spokesperson, "It was discovered that one of the six generators could not operate properly without a part that needed to be manufactured." Because the air conditioning needs to run at full capacity in the Caribbean, "The Captain decided that for passenger comfort, it would be better to change the itinerary."

Of the 557 passengers onboard, less than 30 have returned to the U.K. and will receive a full refund. Those remaining onboard will receive a 40-percent refund.

"Having personally spoken to a great many passengers about our revised plans, I know that -- although some are disappointed about not proceeding as planned -- there is an understanding that this has been beyond our control, and it was better to find out now than in the heat of the Caribbean," said Robin Shaw, chief executive of Saga Shipping.

The cruise -- which departed from Southampton December 7 -- marks Saga Ruby's last sailing before retirement.

The new Mediterranean itinerary includes stops throughout Spain, Italy, France and Portugal. Saga Ruby is scheduled to return to Southampton on January 7.

--by Gina Kramer, Associate Editor