Unregistered passengers could have sneaked inside the stricken liner that crashed off Giglio Island, a civil protection official has claimed.

The numbers of those missing might be higher than previously stated. "There could have been X persons who we don't know about who was inside, who was clandestine," Franco Gabrielli, the national civil protection official in charge of the rescue effort, said.

He quoted relatives of a Hungarian woman as saying that she had called them from the ship and that they had not heard from her since the accident. The woman is not on the list of passengers. Gabrielli said that a woman's body discovered on Saturday night might be of the unregistered passenger.

Meanwhile, authorities are searching for the personal computer of Captain Francesco Schettino. Reports indicate it was taken away by a mystery blonde woman after the disaster.

Schettino claimed sailing to shore for publicity stunts was common practice and was deliberately requested by Costa Concordia's owning company. "The salute to Giglio was arranged and wanted by Costa Crociera before we left Civitavecchia. It was for publicity reasons," reads a copy of Schettino's testimony.

"We have carried out those sail-by salutes all over the world, Sorrento, Capri. I have sailed past Giglio other times - when I was captain of Costa Europa," he added.

The company admitted that staff was aware of Schettino's "character problems" ahead of the accident.

"Schettino may have the odd little character problem, although nothing was ever been reported formally,"Costa Crociera chief executive Pier Luigi Foschi said to Corriere della Sera newspaper, "He was seen as being a little hard on his colleagues. He liked to be in the limelight."

Hordes of ghoulish tourists with picnics and cameras arrived on the island to take pictures of the half-sunken ship.

Around 19 people are still missing. The death toll stands at 13. During the weekend, three badly decomposed corpses were found. The identity of those is still unknown.

A Dutch salvage firm is poised to start pumping out the ship's oil and diesel.