Seven migrants, four of them children, have drowned near the Greek island of Lesbos after their boat collided with a Greek rescue vessel, the coastguard said.
Another person was reported missing, with search crews seeking to locate him.
Earlier on Thursday (local time), officials said they had found the bodies of a woman, two little girls and a baby.
Three other bodies have since been found, "that of a woman, a man and a minor," the coastguard said, as Greek rescuers backed by a Portuguese ship and an EU border agency Frontex helicopter continued to search the waters.
Another 31 people of undisclosed nationality were rescued, the coastguard said. The survivors reported eight people had gone missing.
Officials say an investigation was ordered to determine how the 30-metre patrol vessel collided with the migrant boat, an incident that was caught on AFP camera.
The coastguard said that according to initial findings, the migrant boat had apparently attempted to flee.
The AFP photographer who witnessed the crash caused the migrant boat to sink within just two or three minutes.
Dozens of migrants have died making the perilous Aegean Sea crossing from Turkey to Greece.
On Wednesday, a woman, a young girl and a baby died after their boat sank off Lesbos.
The International Organization for Migration says more than 600,000 migrants have reached Europe's shores since January, while more than 3000 have died or gone missing.
More than 450,000 of the total have arrived in Greece, most of them fleeing the civil war in Syria.
Athens and the UN refugee agency have both called on the European Union to open up more legal channels for people fleeing war and persecution, so that they do not have to risk their lives to reach safety.