Hundreds of people remain missing after a migrant ship went down off the south coast of Greece on Wednesday, as criticism mounted over Europe's years-long failure to prevent such tragedies.

Rescuers pulled 104 survivors from the water and later recovered 78 bodies, but have not located any more since late Wednesday. The Greek coast guard said the search-and-rescue operation would continue beyond the standard 72 hours.

In a joint statement Friday, two United Nations agencies — the International Organization for Migration and the U.N. High Commissioner for Refugees — said that the boat was believed to be carrying anywhere from 400 to 750 people, and that "hundreds remain missing, and feared dead."

The U.N. statement said that the boat had been in distress since Tuesday, but that a search and rescue operation was not initiated until it capsized on Wednesday.

Patrol boats and a helicopter spent Friday scouring the area of the Mediterranean Sea where the packed fishing vessel capsized.

Nine people —all men from Egypt, ranging in age from 20 to 40— were arrested and charged Friday with people smuggling and participating in a criminal enterprise. Twenty-seven of the survivors remain hospitalized, health officials said. The smuggling suspects are due to appear in court Monday.

Greek coast guard spokesman Nikos Alexiou said that coast guard and private ships repeatedly offered by radio and loudspeaker to help the vessel Wednesday while it was in international waters, heading from Libya to Italy, but they were rejected.

Alexiou argued that any effort to tow the overcrowded trawler or move hundreds of unwilling people onto nearby ships would have been too dangerous.

"When you ... try forcibly to tie up to it or to attach a mooring rope, you will have a disturbance, and the people will surge — which, unfortunately is what happened in the end," Alexiou told state-run ERT TV. "You will have caused the accident."

Alexiou also said that, after accepting food from a merchant ship, the trawler's passengers rejected a rope from a second merchant ship "because they thought the whole process was a way for us to take them to Greece."

Greek authorities sent the first ship, the tanker Lucky Sailor, to give the migrants food and water.

The company managing the tanker said Friday that the people on board "were very hesitant to receive any assistance, and at any attempt of approach the boat started to maneuver away."

Eastern Mediterranean Maritime Limited said in a statement that the people on the trawler were eventually persuaded to accept supplies.

The survivors were all boys and men from Egypt, Pakistan, Syria and the Palestinian territories. Alexiou, citing survivor accounts, said passengers in the hold of the fishing boat included women and children but that the number of missing still remained unclear.

Experts said maritime law obligated Greek authorities to attempt a rescue.

They definitely "had a duty to start rescue procedures" given the condition of the vessel, said Erik Røsæg of the University of Oslo's Institute of Private Law. He said a refusal of assistance can be overruled if deemed unreasonable, as it appeared to have been on Wednesday.

The U.N. agencies said that timely maritime search and rescues are "a legal and humanitarian imperative" and called for "urgent and decisive action to prevent further deaths at sea."

Flavio Di Giacomo of the Mediterranean office of the U.N. migration agency tweeted that all migrant boats should be considered dangerous and rescued immediately because "even when they appear to have no problems, in a few minutes they can sink."

A group of nongovernmental organizations, including Amnesty International and Doctors Without Borders, said the EU should "stop seeing solutions solely in the dismantling" of smuggling networks, and set up state-led search-and-rescue operations in the Mediterranean.

"The Greek government had specific responsibilities toward every passenger on the vessel, which was clearly in distress," Adriana Tidona of Amnesty International said. "This is a tragedy of unimaginable proportions, all the more so because it was entirely preventable."

Greece and other southern EU nations that typically are the first destinations for Europe-bound asylum-seekers traveling by sea have toughened border protection measures in recent years, extending walls and intensifying maritime patrols.

"This is a European problem. I think it's time for Europe to be able, in solidarity, to define an effective migration policy for these kinds of situations not to happen again," U.N. Secretary-General Antonio Guterres said during a news conference at U.N. headquarters in New York late Thursday.

The EU's executive commission says the 27-nation bloc is close to an agreement on how member countries can share responsibility in caring for migrants and refugees who undertake the dangerous journey across the Mediterranean.

A judicial investigation is also underway into the causes of the sinking. Greek officials say the vessel capsized minutes after it lost power, speculating that panic among the passengers may have caused the boat to list and roll over.

Most of the survivors were being moved Friday from a storage hangar at the southern port of Kalamata —where relatives also gathered to look for loved ones— to migrant shelters near Athens.

Abdo Sheikhi, a Kurdish Syrian living in Germany, traveled to Kalamata to find out what happened to five family members who were on the boat.

On Friday, he discovered that only his younger brother Ali and another relative had survived. He managed to speak on the phone to Ali, who had been moved to the camp near Athens.

"(Ali) told me he jumped (off the) ship while the others could not jump," Sheikhi said. "They were scared. They were holding on to the boat as it swayed."

Officials at a state-run morgue outside Athens photographed the faces of the victims and gathered DNA samples to start the identification process.

The deadliest capsizing of a migrant boat occurred when a vessel went down off the coast of Libya en route to Italy in April 2015, killing an estimated 1,100 people.

In:
• Greece
• Migrants