Coast Guard Capt. Antonio Morana said the 15-meter (50-foot) boat was carrying 296 people. He said all the victims were believed to be of sub-Saharan origin. According to the survivors, the boat had set sail from Libya two days ago, he said.
Hundreds of people are believed to have died in recent months while attempting the dangerous crossing, fleeing unrest and conflict in Libya and across North Africa. In April, a boat believed to be carrying 300 migrants from Libya capsized, leaving 250 people presumed dead.
The causes of the deaths of the 25 men was not clear, Morana said, 'though ANSA news agency reported they may have died from asphyxiation.
The hold also served as engine room, according to ANSA. As the air became unbreathable, migrants tried to exit but the boat was too packed for those standing above to move aside.
ANSA reported that survivors, including women and children, were taken to a migrants center on the island on coastguard vessels. The bodies were taken ashore and placed in plastic bags on the deck.