AMNA NAWAZ: It's been one week since an overloaded fishing trawler filled with hundreds of migrants sank off the Southwest Coast of Greece.

The vessel left poured in Libya and crossed the Mediterranean before becoming disabled.

It drifted for hours before capsizing.

The anger, grief and political fallout continue.

Hundreds remain unaccounted for.

Special correspondent Malcolm Brabant has spent years reporting on these desperate journeys, and he sent us this update.

MALCOLM BRABANT: This video from a European border force patrol plane shows the fishing boat drifting before it capsized and sank.

Around 600 are still missing and feared drowned, among them, women and children trapped below decks.

Just over 100 survivors have been rescued, all of them men.

GILLIAN TRIGGS, Assistant Secretary-General, UNHCR: I think that the sinking of This relatively small and seriously overloaded fishing vessel and the apparent loss of between 400 and 750 people, this is, I believe, one of the worst over recent years, if not the worst.

MALCOLM BRABANT: Gillian Triggs is the U.N.

Refugee Agency's assistant secretary-general with special responsibility for the protection of those in peril.

She says the death rate among those trying to reach Europe is rising.

GILLIAN TRIGGS: We are concerned that people are even more desperate now.

They will take these voyages knowing full well what the risks are.

When we ask people who've survived these shipwrecks, they will all say that they're well aware of the risks, but they are so desperate that this is what they will choose to do, including with their families.

MALCOLM BRABANT: The Greek authorities say they will continue a search for bodies as long as is necessary.

But there's no hope of finding anyone alive.

Survivors are recovering in a refugee camp near Athens.

Adil Hussain, originally from Pakistan, is looking for a friend of his brother, who was also on the boat.

ADIL HUSSAIN, Brother of Missing Migrant (through translator): I don't know where my brother is.

He is, I don't know, missing.

My brother left Libya last Friday, three days.

I can't find him.

No one will tell me.

MALCOLM BRABANT: Hussain last spoke to his brother just after he boarded the vessel in Libya, where migrants are frequently terrorized before embarkation.

ADIL HUSSAIN (through translator): As soon as he got into the boat, he said only 50 people will fit and they were putting 750 on board.

He said it's 100 percent sure it will take in water.

I told him to get off, don't go.

And he said: "The mafia won't let us.

They have guns.

They have knives."

They were forcing people in.

MALCOLM BRABANT: Many of the victims came from Pakistan.

The family of 25-year-old Shehryar Sultan said he was tricked into believing the trip to Europe would take two to three days.

ADNAN IFTIKHAR (Cousin of Missing Migrant): We just heard the news recently, about two or three hours ago, that it had been confirmed that the dead body of the -- Sultan's companion has been found.

MALCOLM BRABANT: Nine Egyptian men, plucked from the water have been charged in connection with the shipwreck and are in pretrial custody.

The traffickers charged $4,500 passenger and stood to make over $3 million.

The suspects all deny wrongdoing.

Where does the fault lie?

Is it the smugglers, or is there culpability elsewhere?

GILLIAN TRIGGS: Well, clearly, we're concerned about people smugglers, criminal elements, trafficking, and we fully support efforts to manage that element of crime.

But accountability rests in so many areas.

And we need a joined-up European and North African approach, so that we have more reliable search-and-rescue, more reliable disembarkation, and ultimately redistribution of people in need of international protection.

MALCOLM BRABANT: Greece is facing a barrage of criticism.

It's Coast Guard was alerted to the stricken vessel 15 hours before it went down.

This picture was taken from a Coast Guard cutter.

Greece has denied claims that the fishing boat capsized during an attempted tow.

The disaster has appalled Craig Spencer, an emergency doctor from Rhode Island.

Spencer spent six months in the Mediterranean on board the Aquarius rescue ship, where the safety of migrants in distress was paramount.

DR. CRAIG SPENCER, Brown University: I don't think any of us can imagine what its like getting your small child and putting them on a boat in the middle of the night without food, without water, on an unseaworthy vessel, that that being your only option, and to be confronted by a Coast Guard that is responsible under international and national maritime law to save lives at sea.

It's just -- it's truly unbelievable.

MALCOLM BRABANT: Greece is under fire because of its hard-line anti-migrant policy, including proven cases of so called pushbacks, where rescued refugees have been taken back out to sea, in stark comparison to the Italians, who honor their obligations under international law.

As far as you can tell, is this a consequence of Greece's well-documented pushback policy?

GILLIAN TRIGGS: I can't give you a definitive answer to that until we see the results of the investigation.

But what I can say is that countries on the front line, some of them in particular, have not accepted their responsibility for search-and-rescue.

They have pushed back both at land frontiers and at and sea borders.

MALCOLM BRABANT: The European Union has pledged more than $15 billion to bolster its migration policy.

Much of Europe is exasperated by the never-ending flow of migrants.

But, despite the risks, they keep on coming.

For the "PBS NewsHour," I'm Malcolm Brabant.