Dozens of migrants drowned on Friday after their boat capsized off the coast of Tunisia, a monitoring group reported, the latest disaster on a perilous but frequently used crossing in the Mediterranean.

At least 50 people were killed, according to the International Organization for Migration, the United Nations migration agency, and 16 people were rescued. Most of those who died were reportedly from sub-Saharan Africa.

The boat left from Zuwara, Libya, the Tunisian Ministry of Defense said in a statement, and was headed toward Italy when it capsized about 40 miles from the coastal city of Sfax.

The movement of refugees and migrants from Northern Africa and the Middle East across the Mediterranean has dropped significantly from its peak in 2015, when more than one million people traveled the route, but it has remained deadly.