Almost 40 people are feared to have drowned, including four women and a baby, after a dinghy they were travelling in sank off the Canary Islands in the Atlantic Ocean.
Spanish non-profit group Walking Borders said about 39 migrants were believed to have died in the incident on Wednesday.
The coastguard said workers had recovered the body of a child and rescued 24 other migrants from the ocean.
Walking Borders tracks migrant deaths and provides assistance to relatives, posted on Twitter that the dead included four women and a baby.
The group's founder Helena Maleno said the migrants had waited more than 12 hours for assistance.
A Spanish helicopter sent to the area in response to a request for help from Moroccan authorities found the dead child and saw no other survivors, a coastguard spokeswoman said.
A Moroccan patrol boat rescued 24 people, she said. It was not known how many people were on board the vessel, she added.
There was no immediate reaction from Moroccan authorities.
The sinking happened about 160km south-east of Spain's Gran Canaria.
The migrant route from West Africa to the Canary Islands across the Atlantic has become more popular in recent years as authorities have cracked down on illegal migration in the Mediterranean.
The Atlantic is notorious for strong currents that make the trips perilous.
Rescuers on Tuesday found the body of a pregnant woman on board a boat that was carrying some 50 migrants off the Canaries.
Spain is a major gateway for migrants seeking a better life in Europe.
Over 11,200 have died or disappeared since 2018 while trying to reach Spain by sea, according to a report published by Walking Borders last year.
Last week at least 82 migrants died when the boat taking them from Libya to Italy capsized off the coast of Greece.
Authorities still have no clear idea how many people were aboard when it sank – estimates range from 400 to over 700 – making it one of the deadliest accidents involving migrants in the Mediterranean.
Police have arrested nine Egyptians on suspicion of people smuggling – one of them the captain of the boat.
