About 30 migrants are presumed to have drowned off the coast of Libya earlier this week, an Italian prosecutor said Friday, slightly lowering the death toll suggested earlier by humanitarian organizations, dpa reported. Siracusa Prosecutor Francesco Paolo Giordano, who opened an investigation on the incident, said two people who acted as skippers on the migrants' dinghy were among those who are thought to have perished. "By interrogating survivors, we managed to work out what happened. People supposedly fell in the sea during rescue operations, when their dinghy was already taking in water: probably they miscalculated the distance from the cargo ship that rescued them," he said. Some 88 sub-Saharan migrants were disembarked Thursday by a German navy vessel in the Sicilian port of Augusta, and spoke first to volunteers from the UN agency for refugees, UNHCR, the International Organization for Migration (IOM) and the Save the Children charity. "We heard from them that 35 to 40 people died," Giovanna Di Benedetto, a spokeswoman for Save the Children, told dpa earlier Friday.