The death toll has risen to "at least 112" after a boat packed with migrants sank off the coast of Tunisia on Saturday, the International Organization for Migration (IOM) says.
On Sunday, it was reported that some 50 people had died after it capsized.
Sixty-eight others - from Tunisia and elsewhere - were rescued by the coastguard.
The country has become an important new route for migrants trying to make the crossing to Europe in the past year.
This comes after moves were made in neighbouring Libya against human traffickers, who have regularly enslaved, tortured or murdered migrants.
Breaking: at least 112 people died after a boat carrying around 180 migrants sank off the coast of Tunisia on Saturday.— IOM - UN Migration (@UNmigration) June 4, 2018
Of the 180 passengers aboard the boat, about 100 were Tunisian.
The Interior Minister says 55 bodies have been recovered, but the death toll is expected to rise with dozens are still missing.
It was five miles from the Kerkennah Islands and 16 nautical miles from the city of Sfax, the interior ministry said.
One survivor told Reuters news agency that the captain had abandoned the boat after it started sinking to escape arrest by the coastguard.
Each passenger on the fishing boat paid between €600 and €1,000 ($700-$1,170; £530-£880), an IOM spokesman told the AFP news agency.
Unemployed Tunisians and other Africans often seek to cross the Mediterranean sea in makeshift boats from Tunisia to Sicily in Italy.
More than 32,000 people have reached Europe by sea so far this year, the IOM says, and 660 people have died attempting the crossing.