As many as 57 people died after a ship from Gambia carrying about 150 migrants sank on Wednesday off the coast of Mauritania, the United Nations migration agency said.

The sea passage from West Africa to Europe was once a major route for migrants seeking jobs and prosperity. After Spain stepped up naval patrols about 15 years ago, fewer ships carrying African migrants have attempted the perilous journey.

The sinking of the vessel from Gambia was one of the deadliest incidents since migrants found other routes to Europe.

“Mauritanian authorities say up to 57 people are dead after a vessel carrying migrants sank off its coast today,” the United Nations agency, the International Organization for Migration, said on Twitter. Survivors of the sinking told officials that the ship had left Gambia a week ago.