ROME (AP) — Italian naval divers today 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.

Prosecutors, meanwhile, prepared to question the captain, who is accused of causing the wreck that left at least six dead and abandoning the Costa Concordia before all 4,200 people onboard were safely evacuated after the vessel capsized Friday night.

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 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.

The cruiseliner tragedy also has turned into a potential environmental crisis, with rough seas battering the stricken ship raising fears that fuel might leak into pristine waters off Giglio that are part of a sanctuary for dolphins, porpoises and whales.

Waters were relatively calm today.

The Italian Coast Guard on Monday raised the number of missing to 25 passengers and four crew. The missing appear to include a group of Germans, two Americans and six Italians. Family members have identified the Americans as Jerry Heil, 69, and his wife Barbara, 70, from White Bear Lake, Minn.

Italian Coast Guard official Marco Brusco said today there was still “a glimmer of hope” survivors could still be found on parts of the vast ship not yet searched. The last survivor, a crewman who had broken his leg, was rescued Sunday.

The ship is carrying some 500,000 gallons 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 ship’s operator, Costa Crociere SpA, has enlisted one of the world’s leading salvagers, Smit of Rotterdam, Netherlands, to handle the removal of the 1,000-foot ship and extract the fuel safely.

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.

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