A boat carrying some 30 illegal immigrants was feared to have sunk in rough Mediterranean seas after Maltese armed forces said they had called off a search for the vessel on Thursday.
The small, crowded, open boat was reported by a ship to be some 50 miles south of the island of Malta on Monday evening but a search yielded no results.
Italian and US aircraft took part in the search but also later withdrew.
"No trace of the boat was found. We can't say the migrants are presumed dead because they may have landed elsewhere although we would probably have been informed," a spokesman for the Maltese armed forces said.
Scores of illegal migrants have died in recent years in the Mediterranean when overcrowded boats capsized or sank.
The failure to find the boat comes after 37 African shipwreck victims had to wait three weeks before Italy allowed the ship which rescued them to dock in Sicily.
The German humanitarian aid boat Cap Anamur was allowed to dock in Porto Empedocle on Monday. The Africans were transported to a holding centre while the captain on the boat and two others were arrested on charges of aiding and abetting illegal entry.
Italy's highest court ruled on Thursday that Prime Minister Silvion Berlusconi's government had to change tough restrictions on immigration because they were illegal.
Migrants coming from North Africa, mostly Tunisia and Libya, have flooded into southern Italy and Malta in the past few weeks encouraged by fine weather. But the central Mediterranean has seen strong winds and rough seas over the past few days.
Around 400 illegal migrants have arrived on Malta so far this year, mostly in June and July.