Dozens of people are feared drowned after a migrant boat sank near Spain's Canary Islands on Wednesday, according to Spanish officials and aid group Walking Borders.

Authorities have recovered two bodies, including a young boy, but the true number of those who were on board is not known.

Helena Maleno, the founder of Walking Borders, told CNN that her group received desperate calls on Tuesday afternoon from relatives of migrants aboard, saying that the boat was drifting after losing all its engine power. The organization alerted Spanish authorities to request a rescue operation.

Spain's Maritime rescue service tweeted Wednesday that two bodies were recovered from the sunken boat that had departed from Blaya, Morocco. It added that a Moroccan patrol boat had rescued 24 others alive.

Maleno told CNN one of the bodies recovered was a 4-year-old boy, whose body has been taken to Spain. She added that her group believes 37 others on that same boat drowned, based on phone calls with relatives and with people aboard the boat before it sank.

A total of 5,914 migrants have arrived by boat to the Canary Islands this year through June 15, a 31% decline from the same period last year, Spain's interior ministry recently reported.

Maleno said there has been a noticeable increase in recent weeks of attempted migrant crossings to the Canaries.

On Thursday, Spanish government maritime services rescued 227 other migrants from four boats off Lanzarote and Gran Canary islands on Thursday, which are part of the Canaries archipelago off Morocco's west coast.

The incident raises further questions about Europe's response to migration, after an overcrowded fishing trawler -- carrying a reported 750 people -- capsized off the coast of Greece last week, killing at least 82 people and leaving hundreds more missing.