Sixty-three migrants are believed to have died after a boat from Senegal was found off West Africa's Cape Verde islands, the International Organisation for Migration said on Wednesday.
About 38 people survived the tragedy, including four children aged between 12 and 16, IOM spokeswoman Safa Msehli told reporters.
The pirogue, a long wooden fishing vessel, was seen on Monday in the Atlantic Ocean, about 277km from the Cape Verdean island of Sal, police said.
The Spanish fishing vessel that saw it alerted Cape Verdean authorities.
The Cape Verde archipelago is about 600km off the coast on the maritime migration route to the Spanish Canary Islands, which are a gateway to the EU.
Emergency services recovered the remains of seven people, Ms Msehli told AFP, while another 56 people are believed to be missing.
"Generally, when people are reported missing following a shipwreck, they are presumed dead," she said.
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The boat left the Senegalese fishing village of Fasse Boye on July 10 with 101 people on board, Senegal's Foreign Ministry said on Tuesday, quoting survivors.
Apart from one person from Guinea-Bissau, they were all Senegalese.
The authorities have not, for the moment, said what happened to the boat after it set off.
"Those missing are all dead," Abdou Karim Sarr, an officer with the local fisherman's association the CLPA, told reporters.
Moda Samb, a local elected official from Fasse Boye, said nearly all those on the boat had grown up in the fishing community.
"One of the survivors who had his father on the telephone told him that the others were dead," Mr Samb said.
Other families were still waiting to hear if their children were among the survivors, he said.
The authorities in Cape Verde said they had sent the necessary resources to care for the survivors, seven of whom had to be admitted to hospital after reaching Sal on Tuesday.
Senegal's Foreign Ministry said it would be working to repatriate its citizens as soon as possible.
Senegal has dealt with several similar tragedies in recent years.
Cape Verde is on one of the migration routes used by thousands of Africans fleeing poverty and war towards Europe.
Many of them aim to reach the Spanish Canary Islands, one of the most dangerous routes, often travelling in the pirogue boats, which are vulnerable to the weather.
About 90 migrants from Senegal, Gambia, Guinea-Bissau and Sierra Leone had to be rescued in the seas off Cape Verde in January this year.
