A rescue that came too late

A woman migrant cries after being rescued by Spanish aid workers on Tuesday.

(CNN) – They were crowded into a small rubber boat and pushed out to sea. Like so many other similar journeys, not everyone made it.

Showing signs of physical and mental trauma, 167 migrants, most from sub-Saharan Africa, were rescued off the northwest coast of Libya on Tuesday.

Another 13 – including two pregnant women and a couple whose four children survived – perished just 24 hours after setting off on a boat bound for Europe.

Early on in the rescue operation when Spanish NGO Proactiva Open Arms started to move the migrants out of the boat and into the safety of the rescue craft, they found bodies strewn across the bottom of the vessel.

“We are here to rescue people… and when you realize people died, you are there, you know their real situation, you feel the strong reality of the situation,” Proactiva Open Arms mission leader Riccardo Gatti told CNN.

During the rescue, some of the survivors said that another three bodies had been thrown overboard the night before due to overcrowding. Those bodies have yet to be recovered.

It was one of the worst conditions of overcrowding the rescuers said they have seen.

Hampered by rough waters, they first spotted the boat floating adrift around 15 miles north of Sabratha, a coastal city in northwest Libya.

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Volunteers passed life vests to the surviving migrants against the pull of the choppy sea.

“They were so nervous and just wanted to get out of the boat as soon as possible,” Gatti told CNN.

Six young children on board were rescued, the eldest of whom was five years old.

The youngest migrants – exhausted and in shock – slept all day and night.

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Of the 167 rescued survivors, 40 were female. Two women told medical staff on the rescue mission that they were sexually abused several times and “completely beaten” before leaving from Libya, according to Gatti.

Since the start of this year, 2,361 migrants have died on the treacherous route, according to the International Organization for Migration; 112,018 reached European shores.

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Last year, at least 3,800 migrants died on the same route – the highest number recorded since records began.

CNN’s Clint Alwahab contributed to this report.