A man (C) and his daughter (2nd L), both rescued from the Norman Atlantic ferry, disembark from a Greek Airforce C-130 military cargo aircraft at the Elefsina military airport near Athens December 29, 2014. [Photo/Agencies]

"Notwithstanding the weather and the darkness, which is another factor, we persisted throughout the entire night," Pettorino told Sky TG24.

Greek Prime Minister Antonis Samras said the "massive and unprecedented operation saved the lives of hundreds of passengers following the fire on the ship in the Adriatic Sea _ under the most difficult circumstances," while Renzi said the "impressive" rescue efforts prevented "a slaughter at sea."

Passenger accounts emerging Monday painted a picture of a panicked reaction as the fire spread, with passengers choking on the smoke and struggling to figure out how to reach safety as they suffered both searing heat from the ship's floors and driving rain outside.

Prosecutors in Bari were opening an investigation into how the fire started. The damaged ferry itself was to be taken eventually to a northern Adriatic port, but officials said it had not yet been determined which one.

A Greek truck driver, reached by The Associated Press aboard one of the rescue vessels, described the rescue scene as "a chaos, a panic." He said the fire alarm came after most passengers, alerted by smoke filling their cabins, had gone outside, and that there was no crew in sight to direct passengers.

"Our feet were burning and from the feet up we were soaked," Christos Perlis, 32, said by telephone.

When rescue helicopters arrived, Perlis said passengers began to panic.