More than 60 mostly Senegalese people are feared dead after their boat was found drifting about 300km (186 miles) from the Atlantic island nation of Cape Verde.
Seven out of 38 survivors are receiving treatment in hospital.
Their wooden fishing boat was found a month after it set off from Senegal with more than 100 migrants on board.It’s not known what happened to those missing.
Officials in Senegal said they were making arrangements to bring survivors home. Cape Verde officials have called for global action on migration to help prevent further loss of life.
It’s thought the vessel was aiming for the Spanish Canary Islands, a frequent migrant gateway to the European Union.
It was first spotted on Monday by a Spanish fishing boat.
The survivors include four children aged between 12 and 16, a spokesperson for the International Organization for Migration (IOM) said.