At least 20 African migrants trying to reach Europe died Thursday when their boat sank off the coast of Tunisia, Tunisian authorities said.

Tunisian Defense Ministry spokesman Mohamed Ben Zekri said fisherman discovered the bodies off the coastal city of Sfax. He said that five passengers were rescued and about 20 others were still missing.

The boat was crossing the Mediterranean Sea en route to the Italian island of Lampedusa when it sank. National Guard spokesman Ali Ayari said the boat was overcrowded and in poor condition as it faced strong winds, factors he said may have contributed to the sinking.

Refugees and migrants are rescued by members of the Spanish NGO Proactiva Open Arms, after leaving Libya trying to reach…Migrant Deaths Top 3,000 This YearMore than half migrant fatalities this year occurred within and on route to Europe

Tunisian navy units were searching for more survivors, officials said.

In addition to the coast of neighboring Libya, the coastline near Sfax has become a popular departure location for people fleeing poverty and violence in Africa and the Middle East in search of a better life in Europe.

A growing number of Tunisians grappling with economic difficulties in their country are also fleeing despite efforts by Rome to negotiate a halt to the crossings. Most migrants arriving in Italy this year were Tunisians.

Of the more than 34,000 migrants who arrived in Italy this year, more than 12,800, or 38%, were Tunisian. Bangladeshis were the next largest group, followed by migrants from Ivory Coast, Algeria, Pakistan and Egypt.