ROME (AP) -- Italian naval divers on Tuesday exploded holes in the hull of a cruise ship grounded off a Tuscan island to speed the search for 29 missing people while seas were still calm. One official said there was still a "glimmer of hope" that survivors could be found.
A Dutch shipwreck salvage firm, meanwhile, said it would take its engineers and divers two to four weeks to extract the 500,000 gallons of fuel aboard the Costa Concordia, which ran aground Friday. The safe removal of the fuel has become a priority second only to the location of the missing, as the wreckage site lies in a maritime sanctuary for dolphins, porpoises and whales.
As the search intensified, prosecutors were questioning the captain, who is accused of causing the wreck that left at least six dead and abandoning the Concordia before all 4,200 people onboard were safely evacuated after the vessel capsized.
Navy spokesman Alessandro Busonero told Sky TV 24 the holes will help divers enter the wreck more easily. "We are rushing against time," he said.
The divers set four microcharges above and below the surface of the water, Busonero said. Television footage showed one hole above the waterline to be less than two meters (6 feet) in diameter.
"The hope is that the ship is empty and that the people are somewhere else, or if they are inside that they found a safe place to await rescue," Coast Guard spokesman Filippo Marini told Sky TV 24
Waters were relatively calm Tuesday with waves of just 30 centimeters, but they were expected to reach 1.8 meters Wednesday, according to meteorological forecasts.
Smit, the Dutch fuel extraction firm, said there had been no leaks from any of the liner's fuel tanks and that that the tanks appeared intact. While there is a risk that the ship could shift, to date it has been relatively stable perched on top of rocks near Giglio's port.
Smit's operations manager, Kees van Essen, said the company was confident that the fuel could safely be extracted through a system of pumps and valves that vacuum the oil out to waiting tanks. "But there are always environmental risks in these types of operations," he told reporters.
Preliminary phases of the fuel extraction could begin as early as Wednesday if approved by Italian officials, said the Rotterdam, Netherlands-based firm.
The company, which is experienced in both fuel extraction and sunken ship removal, said any discussion about the future fate of the ship -- whether it is removed in one piece or broken up -- would be decided by Italian ship operator Costa Crociere and its insurance companies.
The Italian Coast Guard on Monday raised the number of missing to 25 passengers and four crew. Italian officials gave the breakdown as: 14 Germans, six Italians, four French, two Americans, one Hungarian, one Indian and one Peruvian.
Family members have identified the Americans as Jerry Heil, 69, and his wife Barbara, 70, from White Bear Lake, Minnesota.
Italian Coast Guard official Marco Brusco said Tuesday there was still "a glimmer of hope" survivors could still be found on parts of the vast cruise liner not yet searched. The last survivor, a crewman who had broken his leg, was rescued Sunday.
The ship is carrying some 500,000 gallons (1.9 million liters) of fuel on board. To date there's been no word of any leaks, but choppy waters that slightly shifted the wreckage on Monday escalated fears of one and suspended rescue operations for several hours.
The cruise operator has said Capt. Francesco Schettino strayed from the ship's authorized course into waters too close to the perilous reef. The navigational version of a "fly by" was apparently a favor to the chief waiter who is from Giglio and whose parents live on the island, local media reported.
A judge is to decide Tuesday if Schettino should stay jailed.
Miami-based Carnival Corp., which owns the Italian operator, estimated that preliminary losses from having the Concordia out of operation at least through 2012 would be between $85 million and $95 million, along with other costs. The company's share price slumped more than 16 percent Monday.
Costa Crociere chairman and CEO Pier Luigi Foschi said the company would provide Schettino with legal assistance, but he disassociated Costa from his behavior, saying it broke rules. "Capt. Schettino took an initiative of his own will which is contrary to our written rules of conduct," Foschi said.
Foschi didn't respond directly to prosecutors' and passengers' accusations that Schettino abandoned ship before all passengers had been evacuated, but he suggested his conduct wasn't as bad in the hours of the evacuation as has been portrayed. He didn't elaborate.
The Coast Guard said Schettino defied their entreaties to return to his ship as the chaotic evacuation of some 4,200 people was in progress. After the ship's tilt put many life rafts out of service, helicopters plucked to safety dozens of people still aboard, hours after Schettino was seen leaving the vessel.
The captain has insisted in an interview before his jailing that he stayed with the vessel to the end.
He noted that 4,200 people managed to evacuate a listing ship at night within two hours. In addition, the ship's evacuation procedures had been reviewed last November by an outside firm and port authorities and no faults were found, he said.