The Norwegian-flagged Ocean Viking, which is operated jointly by SOS Mediterranee and Doctors Without Borders, sent its own boats to pick up a pregnant woman close to full term, 12 minors and 37 men, all from sub-Saharan Africa.
"God bless you!" one of the men told the rescuers as they passed life vests to the wet and barefoot passengers.
At least two people feeling ill collapsed upon arrival on the Ocean Viking, while three others were soaked in fuel and two were suffering from mild hypothermia. The operation was witnessed by an Associated Press journalist aboard the ship, which found the migrant boat some 14 nautical miles (16 statute miles) from Libya.
The rescue occurred 14 hours after the Ocean Viking as well as Libyan, Italian and Maltese authorities, the United Nations' refugee agency and Moonbird, a humanitarian observation plane, received an email by Alarm Phone, a hotline for migrants. It was an urgent call seeking help for the rubber boat carrying 50 people without a working engine.
The Ocean Viking, which was already in the Libyan search and rescue zone of the central Mediterranean, informed all authorities that it was beginning an active search for the migrant boat. Throughout the morning, the charity ship chased several objects spotted on the horizon, including what turned out to be a floating palm leaf tangled with fishing gear and an empty small fishing boat.
Throughout the morning, the ship tried to contact Libyan officials without success. The AP journalist witnessed at least three phone calls to the Libyan Joint Rescue and Coordination Center that went unanswered.
The blue rubber boat jammed with the migrants was finally spotted on the horizon near a fishing boat at 1:30 p.m. The fishing boat did not respond to radio contact by the Ocean Viking, which then launched its rescue boats.
At 2:30 p.m., the Libyan Coastguard finally answered the phone and the Ocean Viking reported that its crew was in the process of rescuing the migrants.
A European Union plane taking part in the Operation Sophia anti-human trafficking operation flew over the Ocean Viking, the migrant boat and the fishing boat multiple times shortly before the people were rescued.
As required by maritime law, the ship asked Libyan authorities responsible for rescue coordination in that part of the Mediterranean to provide a place of safety to disembark the rescued migrants, but it also made the same request to Italian and Maltese officials. There was no immediate response.
International migration and human rights bodies say Libya is not a place of safety, and Doctors Without Borders does not consider any North African country safe for disembarkation of the migrants.
But for more than a year, migrant rescues performed by non-governmental groups have frequently led to sometimes weeks-long standoffs trying to get European authorities to allow migrants to be landed.