At least three people were killed and rescuers were searching for other victims after an Italian cruise ship carrying more than 4,000 people ran aground and keeled over in shallow waters.
Dozens were injured and around 50 people remained unaccounted for after the 114,500-tonne Costa Concordia hit a sandbar near the island of Giglio off the coast of Tuscany as passengers sat down to dinner on Friday evening.
Passengers spoke of panic and described some people leaping into the sea from the listing ship, which finally came to rest on its side, with decks partly submerged, a few hundred metres from the shore.
Photographs showed a large gash along its side but officials declined to speculate on what had caused the accident in calm seas close to the shore.
They said rescue efforts were continuing after a night-time operation involving helicopters, ships and lifeboats.
We have about 40 men at work and we're expecting specialist diving teams to arrive to check all the interior spaces of the ship, said fire services spokesman Luca Cari.
We don't rule out the possibility that more people will be lost, he said.
But there was confusion around passenger lists.
It's a very complex operation because some of the passengers may have jumped into the sea and not been picked up by rescuers, while others may have been sheltered in private houses and therefore not been identified yet, said Giuseppe Linardi, police chief in the nearby town of Grosseto.
We were sitting down to dinner and we heard this big bang. I think it hit some rocks. There was a lot of panic, the tables overturned, glasses were flying all over the place and we ran for the decks where we put on our lifevests, passenger Maria Parmegiano Alfonsi told Sky Italia television.
Police and passengers quoted on television spoke of people jumping off the 290-metre-long ship, a floating resort hotel with spas, theatres, swimming pools and a discotheque.
We had a blackout and everybody was just screaming. All the passengers were running up and down and then we went to our cabins to get to know what is going on, said another passenger, who did not give his name.
They said we should stay calm, it is nothing, it's just some electrical problem or just some blackout thing.
Several passengers criticised the response to the emergency.
We'll be able to say at the end of the investigation. It would be premature to speculate on this, coastguard spokesman Filippo Marini told SkyTG24 television.
Many of the 3,206 passengers and 1,023 crew were taken to the mainland port of Porto Santo Stefano where they were given shelter in schools, churches and other public buildings.
The website of the ship's operator, Genoa-based Costa Crociere, had apparently collapsed under the volume of searches but the company set up a helpline to answer public enquiries. Costa said it would cooperate fully with authorities.
There was no word on the identities of casualties.
We are going through the list of passengers at a reception centre that's been set up but most of the passengers didn't have their papers with them of course, so it's been difficult to get full identification, an official said.
Most of the passengers were believed to be Italian but people of several other nationalities were thought to be on board. British consular officials travelled to the area.
(Additional reporting by Philip Pullella and James Mackenzie in Rome and Silvia Ognibene in Florence; editing by Andrew Roche)