ATHENS, Greece (AP) — A broad search and rescue operation was underway early Thursday near the eastern Greek island of Lesbos after a boat carrying migrants capsized while heading to the island from the nearby Turkish coast, Greece's coast guard said.

Weather in the area was reported to be good, and it was unclear what caused the boat to overturn early Thursday morning. The coast guard said 23 people ha been rescued. There was no immediate information on the survivors' nationalities or the type of vessel they had been using.

There were no specific reports of missing people, but a sea and land search and rescue operation was continuing, with three coast guard vessels, an air force helicopter and a nearby boat searching for potential further victims.

Greece is one of the main entry points into the European Union for people fleeing conflict and poverty in the Middle East, Africa and Asia, with many making the short but often treacherous journey from the Turkish coast to nearby Greek islands in inflatable dinghies.

The Greek government has cracked down with increased patrols at sea, and many smuggling rings have shifted their operations south, using larger boats to transport people from the northern coast of Africa to southern Greece.