The family of two missing Americans, Gerald and Barbara Heil of White Bear Lake, Minnesota, said it was thankful for perilous attempts to find those still unaccounted for.

“While it is certainly hard for us to see the recovery efforts stall due to the unstable conditions … we are also very concerned for the safety of the Italian coast guard as they continue to put forth a heroic effort in trying to find those who remain missing,” relatives wrote.

Experts say chances of finding survivors are slim.

“I think you have to look at several issues. One is just the hypothermia. If a compartment is flooded, even if there was air, at this point, most of them would have succumbed to the hypothermic problem of the water temperature,” said Butch Hendrick, president of the diving safety company Lifeguard Systems.

Costa Serena, sister ship of the Concordia, sailed by the wreckage Wednesday night, safely navigating the waters around the island of Giglio.

The investigation is focusing on actions by Concordia Capt. Francesco Schettino.

Prosecutor Francesco Verusio has accused the captain of piloting the ship too fast to allow him to react to dangers, causing the shipwreck, according to legal papers.

Judge Valeria Montesarchio’s initial ruling found Schettino changed the ship’s course, steering too close to shore and causing the ship to hit a rock.

The judge said the captain admitted to making a mistake and that, at the time of the collision, he was navigating by sight.

Schettino may face charges including manslaughter, shipwreck and abandoning a ship when passengers were still on board, prosecutors said.

In her preliminary investigation, Montesarchio said there appears to be considerable evidence against the captain, whom she said showed “imprudence and inexperience.”