Some of the four initial survivors told the Tunisian coast guard on Thursday that the boat had sunk off the town of Zarzis, Red Crescent official Mongi Slim told Reuters.
One of the four died later in hospital, Slim said, adding that no more information was available.
At least 65 migrants drowned last May when their boat capsized off the Tunisian coast after they had left Libya hoping to reach Europe.
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