More than 100 migrants in two rubber boats died trying to cross the Mediterranean Sea off the coast of Libya in early September, according to Doctors Without Borders (MSF).
The international aid agency said in a report on its website Monday that most of the migrants were from Sudan, Mali, Nigeria, Cameroon, Ghana, Libya, Algeria and Egypt.
Survivors being treated by the aid group said one of the boats had engine failure, while the other sprang a leak and began to sink.
"There were 165 adults and 20 children on board" the boat that deflated, an unidentified survivor told MSF.
The report said 55 people from that boat were still alive when rescue helicopters arrived and dropped life jackets into the water. It was hours before the Libyan coast guard picked up the survivors from both boats.
"More than 20 children have died, including two 17-month-old twins," the report said, quoting survivors.
MSF said it is treating the migrants at Libyan detention centers, where they are being held. The organization said the staff reported 18 urgent cases, including nine "suffering from extensive chemical burns [on up to 75 percent of their bodies]" from engine fuel. Six people were transferred to hospitals.
"We are extremely worried for our patients. How can they recover when they are locked inside cells in very poor hygiene conditions?" Jai Defranciscis, an MSF nurse working in Misrata in northwest Libya, said in the report.
Instead of receiving the support they need, refugees and migrants are arrested and detained in deplorable living conditions, without basic safeguards or legal recourse, according to the report.
MSF once again called for an end to the "arbitrary detention of thousands of refugees and migrants across Libya."