Rescue squads have blown a series of holes in the body of the stricken liner Costa Concordia as local officials have raised the tally of missing people from 16 to 29.
Explosives were used to allow divers access to flooded lower cabins. Emergency crews were evacuated Monday after the ship slipped lower in the water due to rough seas.
"Now we will have better access to the gathering points on the ship, where it seems there might be more chance of finding someone, dead or alive," firefighters' spokesman Luca Cari told Reuters.
"They will take micro-cameras in there, and we will be simultaneously looking at the few remaining dry areas and also the wet areas," he said.
Fears are growing for the people missing, which include four crew members as well as passengers from the US, Germany, France and Italy. Local coast guard chief Marco Brusco told the BBC there was just a "glimmer of hope" that survivors could be found.
Captain Francesco Schettino, who is accused of suspected manslaughter and of abandoning the ship before everyone else was safe, appeared to have cruised too close to land.
The ship's owners Costa Cruises said the captain made an "unapproved, unauthorised" deviation in course. Witnesses claim he wanted to show the island to a Giglio native, saying "Look, there's your island".
Prosecutors also claim that he was responsible for the disaster. "The captain is in a very difficult position because we are sure enough that he abandoned the ship when many passengers were still waiting to be evacuated," said prosecutor Francesco Verusio.
Schettino denied any wrongdoing, saying the rocks it hit were not marked on his nautical chart.
Italian media have suggested that the he may have been taking the Costa Concordia too close to the Tuscan island of Guglio to put on a show for the islanders, a bravura "salute" to residents there.
A judge is due to decide on Tuesday if the captain should remain in custody.
Meanwhile, Environment minister Corrado Clini announced that he would declare a state of emergency because of the risk of fuel leaking from the ship's hull.