Kassem Abu Zeed caught the first flight from Germany to Greece after realising his wife and brother-in-law were aboard a trawler crammed with migrants that went down in the Mediterranean Sea.
As rescue ships fanned out Thursday in search of hundreds of people missing in the tragedy, relatives of the migrants gathered in the southern port city of Kalamata to look for their loved ones.
"The last time we spoke was eight days ago, and (my wife) told me that she was getting ready to get on the boat," Abu Zeed told The Associated Press.
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"She had paid $US5000 ($7265)" to smugglers "and then we all know what happened."
Abu Zeed, a 34-year-old Syrian refugee living in Hamburg, said Esra Aoun, 21, and her 19-year-old brother, Abdullah, risked the dangerous crossing from Libya to Italy after they failed to find a legal way to join him in Germany.
Greek authorities have been criticised for not moving to rescue the overcrowded boat's passengers, even though a coast guard vessel escorted it for hours and watched helplessly as it sank in minutes.
Greek officials argued that the migrants repeatedly refused assistance and insisted on continuing to Italy, but legal experts say that's no excuse.
In other developments, nine survivors were arrested on suspicion of belonging to the smuggling ring that arranged the voyage, the coast guard said. State-run ERT TV said the suspects were all Egyptian nationals.
The chances that Abu Zeed's wife survived the sinking, which killed at least 78, were low.
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A huge search-and-rescue operation involving a dozen ships and three aircraft found no survivors since its initial phase early Wednesday, when 104 people were rescued.
None of the survivors were women. Now Abu Zeed hopes Abdullah may be among the men from Syria, Egypt, Pakistan and the Palestinian territories now temporarily housed in a Kalamata warehouse or recuperating in hospitals from hypothermia and exposure.
"The chances of finding (more survivors) are minimal," retired Greek coast guard Admiral Nikos Spanos told state-run ERT television.
Authorities fear that hundreds of people, including many women and children, were trapped below deck when the trawler capsized in the night in deep waters about 75 kilometres offshore.
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The UN migration agency, known as IOM, estimated that the vessel was carrying 700 to 750 people, including at least 40 children, based on interviews with survivors.
That could make the sinking one of the deadliest ever recorded in the central Mediterranean.
Erasmia Roumana, head of a United Nations refugee agency delegation, said the survivors were in shock.
"They want to get in touch with their families to tell them they are OK, and they keep asking about the missing. Many have friends and relatives unaccounted for," Roumana said.
Mohamed Abdi Marwan, who spoke by phone from Kobani, a Kurdish majority town in northeastern Syria, said five of his relatives were on the boat, including a 14-year-old. Marwan said he's heard nothing about them since the vessel sank.
He believes his nephew Ali Sheikhi, 29, is alive, after family members spotted him in photos of survivors, but that has not been confirmed.
"Those smugglers were supposed to only have 500 on the boat and now we hear there were 750. What is this? Are they cattle or humans? How can they do this?" Marwan said.
He said each of his relatives paid $US6000 ($8715) for the trip.
Greece declared three days of mourning, and a Supreme Court prosecutor ordered an investigation.
Greek authorities said the vessel appeared to be sailing normally until shortly before it sank and refused repeated rescue offers. But a network of activists said they received repeated distress calls from the vessel during the same time.
The Greek coastguard said it was notified of the boat's presence late Tuesday morning and observed by helicopter that it was "sailing on a steady course" at 6pm.
A little later, Greek search-and-rescue officials reached someone on the boat by satellite phone, who repeatedly said that passengers needed food and water but wanted to continue to Italy, it said.
Merchant ships delivered supplies and observed the vessel until early Wednesday morning, when the satellite phone user reported a problem with the engine. About 40 minutes later, according to the coastguard statement, the migrant vessel suddenly began to rock violently and sank.
Coastguard experts believe the boat may have run out of fuel or experienced engine trouble, with movement of passengers causing it to list and capsize.
Alarm Phone, a network of activists that provides a hotline for migrants in trouble, said the problems began much earlier in the day. The network said it was contacted by people on the vessel seeking help shortly after 3pm. They said they "cannot survive the night".
Around 6.20pm, Alarm Phone wrote, migrants reported the vessel was not moving and that the captain had left on a small boat. The two accounts could not immediately be reconciled.
Experts said maritime law would have required Greek authorities to attempt a rescue if the boat was unsafe, regardless of whether passengers requested it. Search and rescue "is not a two-way contract. You don't need consent", retired Italian coast guard Admiral Vittorio Alessandro said.
An aerial photograph of the vessel before it sank released by Greek authorities showed people crammed on the deck. Most were not wearing life jackets.
Overcrowding, a lack of life vests, or the absence of a captain would have all been reasons to intervene, Alessandro said.
Professor Erik Røsæg from the University of Oslo's Institute of Private Law said that under international law, Greek authorities definitely "had a duty to start rescue procedures" given the condition of the trawler.
He said a captain's refusal of assistance can be overruled if deemed unreasonable.
"It appears that the refusal in this case was highly unreasonable," Røsæg said.
Greece's caretaker minister for civil protection, Evangelos Tournas, defended the coastguard's conduct.
"The coastguard cannot intervene with a vessel which doesn't accept the intervention in international waters," he said.
"Consider also that an intervention by the coastguard could have placed an overloaded vessel in danger, which could capsize as a result."
The bodies of the dead migrants were moved to a morgue outside Athens, where the identification process will start.
The location of the sinking is close to the deepest part of the Mediterranean Sea, where depths of up to 5.2 kilomtres could hamper any effort to locate a sunken vessel.
Ursula von der Leyen, the European Commission president, promised to strengthen cooperation between the European Union and nearby countries to try to further crack down on migrant smugglers.
But human rights groups say the crackdown has forced migrants and refugees to take longer, more dangerous routes to reach safe countries.
Eftychia Georgiadi, an official in Greece with the International Rescue Committee charity, said the disaster should serve as a wake-up call to the EU.
"Nobody embarks on these treacherous journeys unless they feel they have no other option," she said.
The EU's failure to offer more safe pathways to migration "effectively slams the door on people seeking protection".
The IOM has recorded more than 21,000 deaths and disappearances in the central Mediterranean since 2014.
The Mediterranean's deadliest shipwreck in living memory occurred on April 18, 2015, when a fishing boat overcrowded with migrants collided off Libya with a freighter trying to come to its rescue.
Only 28 people survived. Forensic experts concluded that there were originally 1100 people on board.
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