Two dock workers were thrown into the water in a new mishap Wednesday involving a Carnival cruise ship, which broke free from moorings in a US port, the company said.

One worker was reported missing after high winds caused the Carnival Triumph to break free in the Gulf Coast port of Mobile, Alabama, where it was docked after a hellish four-day ordeal last month.

Television pictures showed a large hole on the stern of the ship, apparently on a passenger deck half way up the side of the vessel.

All Triumph employees were accounted for, said Carnival, which has suffered a string of accidents since its cruise ship the Costa Concordia capsized off the Italian coast last year, killing 32 people.

"Due to strong winds that reached speeds exceeding 70 miles per hour (113 km/h) during a severe storm in Mobile, Alabama, Carnival Triumph, which was in wet dock at a Mobile shipyard, broke away from its moorings," said a Carnival statement.

"The ship drifted and is now secure. It is expected to soon be moved to the Mobile Cruise Terminal. There are a number of tug boats on site, as well as the US Coast Guard and Mobile authorities.

Two workers on an adjacent pier fell into the water. One was reported missing, and it was unclear by late afternoon if he had been found.

"All Triumph workers and contractors are accounted for," Carnival spokesman Vance Gulliksen told AFP, while adding that the two missing workers were not employees with the Triumph.

The Triumph docked in Mobile last month, after an engine room blaze left the massive vessel without electricity to power the kitchens, toilets, and other necessities for four days.