The Greek coast guard said it had found the bodies of two women and 39 other migrants on the tiny island of Farmakonisi in the Aegean Sea on Monday and that an investigation was underway to determine what had occurred.
The circumstances of the deaths were unclear, they said.
Greek authorities were informed that the migrants had reached the island earlier in the day, just 6 miles (9.7 km) off the Turkish coast, coast guard officials said, adding they were still searching for other survivors of a potential shipwreck.
Those rescued were transferred to the island of Leros nearby.
Greece, in the southeast corner of the European Union, has long been a favoured gateway to Europe for migrants and refugees from the Middle East, Africa, and Asia.
The coast guard has rescued over 250,000 people since 2015, when Greece was at the frontline of Europe’s migration crisis and nearly one million people landed on its islands, including Farmakonisi, from Turkey. Thousands have died at sea, according to the U.N. refugee agency.
This month, at least seven migrants drowned, including one boy, one girl and two women, when their boat sank off the island of Lesbos.
