ATHENS, Greece — Twelve migrants were found dead Friday and a further 15 were rescued after a boat capsized in western Greece, authorities said.

The Merchant Marine Ministry said the victims included four children. The accident occurred early Friday, off the coast of Lefkada, an island in the Ionian Sea. The migrants were presumed to have been headed to nearby Italy from the western Greek mainland.

Ministry officials said the migrants were aboard a plastic boat that was 7 to 8 meters (23 to 26 feet) in length. The survivors were being taken to hospitals for observation.

Lefkada mayor Costas Aravanis said coast guard boats and divers had searched the search in the Palairos area, between Lefkada and the mainland, before the effort was eventually called off about four hours after the sinking was first reported.

"The boat sank after dawn in good weather conditions, with low prevailing winds, so it's unclear how this happened. . . . It looks like the boat had been overloaded," Aravanis told the AP. "Some of the survivors managed to swim to the shore and call for help. . . . There have been cases in the past where smugglers tricked the immigrants and left them on Lefkada, claiming they had arrived in Italy."

It was unclear where the voyage began. Greece is the European Union's busiest transit point for illegal immigration.

"The new tragedy off Lefkada, with victims including young children, confirms the need to immediately implement initiatives taken by the European Union, with Greece's initiative too, to deal with the problem of illegal migration," said government spokesman Simos Kedikoglou.

"Particular emphasis must be placed on eradicating the networks set up by smugglers, who profiteer on the lives of desperate people. Greece has been dealing with waves of illegal migration for years but this is no longer just a Greek problem. The answer must be European."