ATHENS, Greece (AP) — A major search-and-rescue operation launched overnight after a migrant smuggling boat sank off the southern Greek island of Crete continued Tuesday, with survivors unable to say how many people had originally been on board and whether there were people still missing.

Greece’s coast guard said one more person had been rescued in the early hours of Tuesday, bringing the total number of people saved to 57. Three bodies — those of two children and a woman — were recovered from the sea Monday night.

Authorities were alerted after a person claiming to be a passenger on board called an emergency number. It was unclear what type of vessel the migrants were on. The boat sank 12 nautical miles (22 kilometers) east of Crete in rough seas, the coast guard said.

Two coast guard vessels, two aircraft and five ships that had been sailing nearby were participating in the search. The coast guard said survivors were not able to give an account of how many people had been on board initially, and it was unclear whether there were any missing.

Greece is one of the main entry points into the European Union for asylum-seekers and migrants from the Middle East, Asia and Africa. The vast majority cross from the Turkish coast to nearby Greek islands in dinghies. But authorities say they have seen an increase in smuggling gangs using larger boats, such as yachts and sailing boats, to pass south of Crete and head to Italy.