The ship's jailed captain, meanwhile, lost the support of the vessel's Italian owner as he battled prosecutors' claims that he caused the deadly wreck that killed at least six and left 29 missing.
Earlier, authorities had said 16 people were missing. But an Italian Coast Guard official, Marco Brusco, said late Monday that 25 passengers and four crew members were unaccounted for three days after the disaster. He didn't explain the jump, but indicated 10 of the missing are Germans. Two Americans are also among the missing.
At least three families of Italian passengers have said that despite their loved ones' being listed among those safely evacuated, they hadn't heard from them.
There still is "a glimmer of hope" that there could be survivors on parts of the vast Costa Concordia that not have been searched by rescuers, Brusco said. A search of the above-water portion of the ship last yielded a survivor, a crewman who had broken his leg, on Sunday.
Waters that had remained calm for the first three days of the rescue turned choppy Monday, shifting the wreckage of the Costa Concordia and temporarily suspending divers' searches for survivors. A search for bodies was suspended overnight.
Italy's environmental minister raised the alarm about a potential environmental catastrophe if any of the 500,000 gallons (2,300 tons) of fuel begins to leak into the waters off Giglio, which are popular with scuba divers and form part of the protected Tuscan archipelago.
"At the moment there haven't been any fuel leaks, but we have to intervene quickly to avoid an environmental disaster," Corrado Clini told RAI state radio.
Even before the accident there had been mounting calls from environmentalists to restrict passage of large ships in the area.
The ship's operator, Costa Crociere SpA, has enlisted Smit of Rotterdam, Netherlands, one of the world's biggest salvagers, to handle the removal of the 1,000-foot (290-meter) cruise liner. A study could come as early as Tuesday on how to extract the fuel safely.
Smit has a long track record of dealing with wrecks and leaks, including refloating grounded bulk carriers and securing drilling platforms in the aftermath of Hurricane Katrina. A spokesman for Smit did not immediately return calls seeking comment on the Concordia salvage.
The Italian cruise operator said Capt. Francesco Schettino intentionally strayed from the ship's authorized course into waters too close to a perilous reef, causing it to crash late Friday off the tiny island of Giglio and capsize.
The navigational version of a "fly by" was apparently made as a favor to the chief waiter who is from Giglio and whose parents live on the island, local media reported.
A judge on Tuesday is to decide whether Schettino should remain jailed.
"We are struck by the unscrupulousness of the reckless maneuver that the commander of the Costa Concordia made near the island of Giglio," prosecutor Francesco Verusio told reporters. "It was inexcusable."
The head of the U.N. agency on maritime safety said lessons must be learned from the Concordia disaster 100 years after the Titanic rammed into an iceberg, leading to the first international convention on sea safety.
"We should seriously consider the lessons to be learned and, if necessary, re-examine the regulations on the safety of large passenger ships in the light of the findings of the casualty investigation," said Koji Sekimizu, secretary-general of the International Maritime Organization.
Miami-based Carnival Corp., which owns Costa, estimated that preliminary losses from having the Concordia out of operation for at least through 2012 would be between $85 million and $95 million, though it said there would be other costs as well. The company's share price slumped more than 16 percent Monday.
Two of the missing are Americans, identified by their family as Jerry Heil, 69, and his wife Barbara, 70, from White Bear Lake, Minnesota.
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 all rules and regulations.
"Capt. Schettino took an initiative of his own will which is contrary to our written rules of conduct," Foschi said in his first public comments since the grounding.
At a news conference in Genoa, the company's home base, Foschi said that Costa ships have their routes programmed, and alarms go off when they deviate. Those alarms are disabled if the ship's course is manually altered, he said.
"This route was put in correctly upon departure from Civitavecchia," Foschi said, referring to the port outside Rome. "The fact that it left from this course is due solely to a maneuver by the commander that was unapproved, unauthorized and unknown to Costa."
Foschi said only once before had the company approved a "fly by" of this sort off Giglio — last year on the night of Aug. 9-10. In that case, the port
and company had approved it.
Residents, however, said such displays have occurred several times in the past, though always in the summer when the island is full of tourists.
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 Italian coast guard says Schettino defied their entreaties for him to return to his ship as the chaotic evacuation of the 4,200 people aboard was in full progress. After the ship's tilt put many life rafts out of service, helicopters had to pluck to safety dozens of people remaining 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.
Foschi defended the conduct of the crew, while acknowledging that passengers had described a chaotic evacuation where crew members consistently downplayed the seriousness of the situation as the ship lurched to the side.
"All our crew members behaved like heroes. All of them," he said.
He noted that 4,200 people managed to evacuate a lilting 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.
Once on land, the survivors complained that Costa was stingy with assistance.
Blake Miller, on board to celebrate his partner's 50th birthday, said Costa representatives rebuffed his efforts to get some reimbursement so he could buy a change of clothing.
"The Costa representative at our hotel told me, 'you might want to get a lawyer when you get back to the States,'" to pursue reimbursement, Miller told The Associated Press from his hotel in Rome Sunday night, where he was staying at his own expense.
Only passengers who had paid for special insurance to cover lost belongings would receive compensation to buy replacements, he said they were told.
Costa Crociere didn't immediately respond to a phone message or an emailed request for a response.
Miller, from Austin, Texas, said survivors were taken to a hotel near Rome's airport and told Costa would pay for one night's stay and their plane fare home only "if we pack up and leave the country" on Sunday morning.
Miller, who is director of business travel for Intercontinental hotels, said Costa representatives spoke to passengers about potential refunds or free cruise vouchers. But besides what he paid for the cruise, he said he paid several hundred more euros (dollars) for excursions during port calls and drinks on board.
Foschi, the Costa CEO, said he was certain "we'll be able to find a material solution that will make them happy."
Class action suits are a rare novelty in Italy, but Italian consumer advocacy organization Codacons said more than 70 passengers had indicated that they wanted to join a class-action approach to winning compensation from Costa.
"Our aim is to make every passenger obtain an indemnity of at least euro10,000 (more than $12,500) for the material damage suffered and for moral damage, such as the terror suffered, ruined vacations and the grave risks that they ran," said Codacons president Carlo Rienzi.