ROME (AP) — A smuggler's boat crammed with hundreds of people overturned off Libya's coast as rescuers approached, causing what could be the Mediterranean's deadliest known migrant tragedy and intensifying pressure on the European Union Sunday to finally meet demands for decisive action.

Survivor accounts of the number aboard varied, with the Italian Coast Guard saying that the capsized boat had a capacity for "hundreds" of people. Italian prosecutors said a Bangladeshi survivor flown to Sicily for treatment told them 950 people were aboard, including hundreds who had been locked in the hold by smugglers. Earlier, authorities said a survivor told them 700 migrants were on board.

It was not immediately clear if they were referring to the same survivor, and Premier Matteo Renzi said Italian authorities were "not in a position to confirm or verify" how many were on board when the boat set out from Libya.

Eighteen ships joined the rescue effort, but only 28 survivors and 24 bodies had been pulled from the water by nightfall, Renzi said.

These small numbers make more sense if hundreds of people were locked in the hold, because with so much weight down below, "surely the boat would have sunk," said Gen. Antonino Iraso, of the Italian Border Police, which has deployed boats in the operation.

Prosecutor Giovanni Salvi told The Associated Press by phone from the city of Catania that a survivor from Bangladesh described the situation on the fishing boat to prosecutors who interviewed him in a hospital. The man said about 300 people were in the hold, locked in there by the smugglers, when the vessel set out. He said that of the 950 who set out aboard the doomed boat, some 200 were women and several dozen were children.

Salvi stressed that there was no confirmation yet of the man's account and that the investigation was ongoing.

Iraso said the sea in the area is too deep for divers, suggesting that the final toll may never be known. The sea off Libya runs as deep as 3 miles (5 kilometers) or more.

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