The number of migrants asphyxiated in the hold of an overcrowded fishing boat off the Italian coast has climbed to 49, Italian media reported Sunday.
Authorities made the grim discovery on Saturday when an Italian navy patrol boat was sent to the sinking vessel's aid as it made the journey across the Mediterranean to Europe.
At first around 40 people were thought to have died, but the number has been revised upwards to 49, according to reports citing authorities in the Sicilian port of Catania.
Some 312 survivors -- including 45 women and three children -- were pulled off the boat and were to arrive in Catania on Monday aboard the Norwegian vessel Siem Pilot.
According to the Italian newspaper Corriere della Sera, the victims were apparently asphyxiated by fuel fumes and were primarily married men who had given spots on the deck to their wives.
Survivors of the hazardous crossing from Libya often tell of how traffickers lock migrants in the hold who pay less for the voyage -- mostly black Africans.
Packed inside the confined space they not only risk drowning if the boats capsize, but many are also overcome by diesel fumes.
The migrants who attempt the dangerous crossing are fleeing war and poverty in Africa and the Middle East, with many hoping to be granted asylum by European countries.
Also on the Siem Pilot were 103 other migrants rescued on Saturday. Another 201 people rescued by a boat operated by Doctors Without Borders (MSF) were due to arrive on Sunday in Sicily.
More than 103,000 migrants have arrived on Italy's shores since the start of the year while nearly 135,000 have arrived in Greece.
At least 2,300 people have died making the crossing, according to the latest figures issued by the International Organization for Migration (IOM).