The Moldovan-flagged cargo ship Blue Sky M docked in the port of Gallipoli early on Wednesday after the Italian Navy undertook an operation to save some 700 migrants aboard, reports Deutsche Welle.

The ship, headed for the Croatian port of Rijeka, sent a distress signal on Tuesday afternoon, claiming it was drifting out of control off the Greek island of Corfu and there were armed people on board.

As the ship came closer to Italy, port authorities dispatched two helicopters and six coast guard officials to the vessel. Italian coast guard spokesman Filippo Marini said that his team took control of the ship after no crew was found. The media has speculated that the crew were human traffickers who jumped ship when they saw the authorities arriving.

Despite the distress signal, there appeared to be nothing mechanically wrong with the ship. It was most likely activated by one of the migrants, who were in need of food and blankets.

Police and maritime authorities have said they would investigate how the migrants, reportedly mainly from Syria and including a heavily pregnant woman, came to be hidden on the cargo ship.