There was scant information on the dead, most of whom were believed to be Mauritanian nationals, although they included two Senegalese, they said. Four bodies had washed up on shore.
Mauritanian coastguards rescued 14 people on Monday including two women from the vessel when it sank off Cap Blanc shortly after leaving Nouadhibou, Mauritania's second city and biggest port, the sources said.
It was not clear whether the boat sank due to overloading or bad weather, they added.
Six African migrants drowned off the Canary Islands late last month when Tropical Storm Delta sank a makeshift boat carrying around 50 people. In September more than 60 Somali migrants died at sea after smugglers left them helpless for 20 days in a faulty boat during a crossing to Yemen.
Many Africans leave their homelands every year on a hazardous journey in the hope of a better life in Europe or elsewhere, but many do not make it.
Migration has become an even more sensitive issue since a handful of people died in September as a wave of migrants tried to force their way into the Spanish enclave of Ceuta on Africa's northern coast.