ROME • Italy's cruise liner disaster threatened Monday to become an environmental crisis, as rough seas battering the stricken mega-ship raised fears that fuel might leak into pristine waters off Tuscany that are part of a sanctuary for dolphins, porpoises and whales.

Waters that had remained calm for the first three days of the rescue turned choppy Monday, shifting the wreckage of the Costa Concordia a few inches and suspending divers' searches for 29 people still unaccounted for. A retired U.S. couple — Jerry Heil, 69, and his wife, Barbara, 70, of White Bear Lake, Minn. — were among the missing. At least six people were killed.

Italy's environmental minister raised the alarm about a potential ecological catastrophe if any of the 500,000 gallons of fuel begins to leak into the pristine 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 cruise liner. A study could come as early as today on how to extract the fuel safely.

Costa is owned by Miami-based Carnival Corp., which operates 101 ships under several brands including Carnival, Cunard, Holland America, Princess and Seabourn.

The ship's jailed captain, meanwhile, lost the support of his Italian employer as he battled prosecutors' claims that he caused the deadly wreck and abandoned the sinking ship before its 4,200 passengers and crew had been evacuated.

The Italian cruise operator said Capt. Francesco Schettino made an unauthorized deviation that caused the ship to crash late Friday.

The navigational "fly by" of Giglio 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 is to decide today 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 said. "It was inexcusable."

The head of the U.N. agency on maritime safety, meanwhile, 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.

At a news conference in Genoa, the company's home base, Costa Crociere chairman and CEO Pier Luigi Foschi said 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 that 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 had taken place 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 in which crew members consistently played down 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 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.

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 said from his hotel in Rome on Sunday night, where he was staying at his own expense.

Miller, from Austin, Texas, said survivors were taken to a hotel near Rome's airport and were 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.