Italian authorities are considering when to call off the search for survivors aboard the wreck of the cruise liner Costa Concordia, the coast guard said Thursday, as rescuers used explosives to blow new holes in the ship in search of victims.

Authorities are mulling when to change the operation from rescue to recovery, coast guard spokesman Cosimo Nicastro said Thursday. Divers continued their search of the wreck into Thursday evening.

At least 11 people are known to have died in the disaster, and 21 are still missing, according to the Italian Crisis Unit.

Coast guard records published Thursday by an Italian newspaper pile further pressure on the captain of the Concordia and his officers, suggesting that the authorities first became aware of the crash from a friend of the mother of a passenger about 15 minutes after the ship hit rocks.

The coast guard identified the ship in trouble and contacted it, asking if there were problems on board, at 10:14 p.m. -- more than half an hour after the 9:41 p.m. collision -- according to a coast guard log published in the newspaper La Repubblica.

The ship responded that it was experiencing a "black out," according to the log, and said the crew believed it could solve the problem in a short time. The log does not indicate which crew member was speaking.

What appears to be the audio of that first radio call between the Costa Concordia and the coast guard was broadcast on Italian media Thursday.

A coast guard official is heard to ask: "What kind of a problem is it? Just something with the generator? The police of Prato have received a phone call from the relatives of a sailor who said that during the dinner everything was falling on his head."

The unidentified crew member responds: "We have a black out and we are checking the conditions on board."

"The passengers say they have been told to put on the life vests, is this correct?" the coast guard then asks, to which the crew member repeats the same answer, before promising to keep the coast guard updated.

Criticism from both Costa Cruises and the authorities has focused so far on Capt. Francesco Schettino, who is under house arrest and facing possible charges of manslaughter, shipwreck and abandoning ship.

Authorities accuse the captain of piloting the ship too fast to allow him to react to dangers, causing the shipwreck, according to legal papers.

Experts are performing toxicology tests on a sample of his hair, prosecutor Francesco Verusio said Thursday.

Verusio is preparing a motion to have Schettino sent back to jail from house arrest, he said.

Verusio also vowed to investigate the leak of legal documents related to the case, saying they did not come from his office.

Also on Thursday, Italian officials identified two victims as Jeanne Gannard, 70, and Pierre Gregoire, 69, both from France, the Italian Crisis Unit said.

Eight victims have now been named -- four French passengers, a Spanish passenger, and an Italian one, and one crew member each from Hungary and Peru.

Nearly a week after the wreck, it appears increasingly unlikely that any survivors will still be found aboard the ship.

Italian mother Susy Albertini, whose 5-year-old daughter Dayana Arlotti is reportedly the youngest person still missing, is among those desperate for news of their loved ones.