ROSETTA, Egypt — Survivors, some handcuffed to hospital beds, described watching women and children drown after an overcrowded migrant boat capsized off Egypt’s coast, as Egyptian authorities said Thursday 51 bodies had been recovered and an international NGO estimated that over a hundred people were still missing at sea.

Fishermen in boats were first at the scene early Wednesday, an Egyptian official said, and in the more than five hours it took the coast guard to arrive, they rescued dozens of survivors and retrieved bodies.

The capsizing could potentially rank among the deadliest incidents in the migrant route across the Mediterranean. However, the final death toll will require first obtaining a reliable figure for how many people were on board the boat, and more bodies could yet be recovered at sea or along the coast.

Estimates for the number of passengers aboard the boat ranged between 250, 350 and 600. Survivors said most of those who died were women and children.

The International Organization for Migration said the boat carried 350 migrants, but cautioned that the figure was an estimate, according to IOM spokesman Joel A. Millman in Rome. He did not say how the agency arrived at that figure. Quoting unidentified sources, he said the Egyptian coast guard had rescued 163 migrants and recovered 42 bodies, leaving 145 unaccounted for.

“We’re still working to verify what has happened to survivors. I’m sure you can appreciate the difficulties in gathering accurate information in cases like this,’ said Jenny Sparks of IOM in Geneva.

Mohammed Sultan, the governor of Beheira province, where Rosetta is located, told The Associated Press that authorities did not have a precise number for those who were on board the vessel, but that 250-400 seemed likely. He said 157 people were rescued.

Egypt’s state-run Middle East News Agency, MENA, on Wednesday put the number at 600, but did not say where the figure came from.

The U.N. refugee agency said it had received preliminary estimates of around 450 people aboard, with 150 survivors. Spokeswoman Barbara Molinario said the agency hadn’t yet interviewed survivors, which is often a crucial piece of the puzzle in determining passenger numbers. The estimates came from UNHCR’s contacts with Egyptian authorities.

The head of the local council in the area, Ali Abdel-Sattar, said the loss of life would have been much heavier had a fishing vessel not been close by when the boat capsized. He identified the skipper of the fishing boat as Mohammed Abu Hamid.

“If this man wasn’t there, if this man wasn’t sent by God, the entire group of migrants would have been dead by now,” said Abdel-Sattar.

He said the coast guard did not start its rescue operations until 11 a.m. on Wednesday, more than five hours after the boat capsized.

Hassan Suleiman, a relative of one of those who were on board, said authorities were slow to rescue the migrants and that fishing boats were first at the scene, plucking bodies from the water and rescuing survivors. He also claimed that traffickers in the area were known to police by name and that some policemen were paid by them to look the other way.

“This is shameful. This is shameful for our children and our young people that go to them.”

He said migrants go out to sea in small groups and gather at bigger boats, which begin the journey to Europe when traffickers believe they have gathered enough passengers. He said on bigger boats, the space below deck at the front of the vessel is often packed tight with people. “Those are dead, for sure.”

He said smugglers were charging migrants around 35,000 pounds (nearly $4,000) each for the perilous journey to Europe. “They paid money to go and die,” he said.

Egyptian authorities, meanwhile, arrested four people in connection with the incident and issued arrest warrants for five more. They said the four were members of the vessel’s crew and were remanded in police custody for four days pending further investigation. They face charges of human trafficking and manslaughter.

An initial breakdown of the nationalities of the migrants showed that they included 111 Egyptians, mostly teenagers and men in their 20s, said Sultan, the Beheira governor. There were also 25 Sudanese, while the rest were sub-Saharan Africans and Syrians.

Thousands of illegal migrants have made the dangerous sea voyage across the Mediterranean in recent years, fleeing war and poverty in the Middle East and elsewhere.

The number of migrants trying to cross the Mediterranean from Egypt to Europe has increased significantly in the past year, EU border agency Frontex recently said. More than 12,000 migrants arrived in Italy from Egypt between January and September, compared to 7,000 in the same period last year, it said.

Many of the survivors in the latest tragedy were detained briefly by police, before they were released. Some of those rescued after suffering injuries were taken to hospitals, where they lay handcuffed to beds under police guard.

One survivor, Ahmed Darwish, blamed traffickers for the tragedy, saying overcrowding caused the boat to capsize, and accused authorities of not reacting quickly enough.

“The boat is meant to hold 200, and they put 400 in it. And this is what caused the catastrophe,” he said. Many of the dead, he explained, were women and children who could not swim. “Those … that knew how to swim moved away (from the boat), leaving behind women and small children,” he said.

Mina Fawzi, a 19-year-old survivor, told AP that there were already about 250 people on the boat when the smugglers brought along another 250. “With the large number of people, the boat sank,” he said.

Associated Press writers Maggie Michael in Cairo, Nicole Winfield in Rome and Mostafa Hassan in Rosetta, Egypt, contributed to this report.