The Swedish ship Poseidon was already rescuing 130 migrants from a raft north of Libya's coast when it got a call to assist a nearby wooden ship, authorities said. The Swedes rescued 439 survivors from the wooden boat then looked for the bodies.
"We had to cut up the deck of the wooden boat to get to (the bodies) in a safe way," Swedish coast guard spokesman Mattias Lindholm told The Associated Press.
He said the victims probably died of asphyxiation. The corpses were placed in body bags to make sure they didn't come into contact with the survivors.
The Italian coast guard said that in addition to the 51 dead discovered by the Poseidon crew, three women were found dead in another migrant boat and another corpse was found during the 10 rescue operations that were launched Wednesday. The coast guard said around 3,000 people were rescued as Libya-based smugglers took advantage of calm seas to send boats overloaded with migrants to Europe.
Migrants by the tens of thousands are braving the perilous journey across the Mediterranean, fleeing war and poverty in the Middle East, Africa and Asia with the hope of reaching Europe and be granted asylum. They pay Libyan smugglers upward of 1,000 euros ($1,150) to be crammed into overcrowded, unseaworthy boats for the crossing.
The U.N. refugee agency says more than 2,400 people have died at sea so far this year making the crossing. More than 110,000 migrants have been rescued and brought to southern Italian ports.