Officials have conceded that any hopes of finding additional survivors, or even victims, are remote, because the boat sank in one of the deepest spots of the Mediterranean, where the seabed is at a depth of 4,000 meters, or about 2.5 miles.

Nevertheless, the efforts continued on Thursday. “There is no plan to stop the search,” Nikolaos Alexiou, a spokesman for the Greek Coast Guard, told state television. “We’re continuing and the search will broaden.”

The survivors will be moved to a state camp in Malakasa, north of Athens, as soon as processing by coast guard officials has been completed, the migration ministry said.

The survivors, all men, are believed to be from Syria, Egypt and Pakistan. It remained unclear how many women and children might be among the missing.

The nine detainees will be held by the police for 48 hours pending their appearance before an investigating magistrate in Kalamata.