Four people were found dead in a cargo ship that docked at the southern Italian port of Gallipoli on Wednesday after it was rescued by the coast guard, the Italian Red Cross said, according to Reuters. The Moldovan-flagged Blue Sky M, which was reportedly carrying an estimated 900 migrants, was abandoned by the ship’s crew and was put on autopilot.

Italian port authorities reportedly sent two helicopters with six coast guard officials to rescue the ship and seized its control when no crew could be found. The unmanned vessel was approaching the rocky Italian coast at six nautical miles an hour, Filippo Marini, an Italian coast guard commander, said, according to CNN. The coast guard also reportedly said that a collision could have claimed several lives and may have led to a large environmental disaster. Authorities suspected that the people on board the vessel were mostly Syrian and Kurdish migrants.

The exact number of people on board is still not known, Red Cross spokesperson Mimma Antonagi, told Reuters.

There were also unconfirmed reports that passengers were suffering frostbite, the BBC reported. Officials reportedly said that some migrants have been taken to hospital, but their health condition was not known.

The vessel was reportedly spotted close to the coast of Corfu on Tuesday after it issued a distress signal. Authorities said that they will investigate the matter. According to the Marine Traffic, a tracking website, the ship abruptly made a change in direction towards Italy.

The U.N. Refugee Agency reportedly estimated that nearly 200,000 migrants have arrived in Italy and Greece by sea between January and November.

The incident comes just days after a ferry traveling from Greece to Italy caught fire off the Adriatic coast on Sunday, killing at least 10 passengers. More than 400 people were rescued from the Norman Atlantic ferry.