MILAN — The feared drowning of 400 migrants in a shipwreck this week in the Mediterranean Sea — one of the deadliest such tragedies in the past decade — raised alarms Wednesday amid an unprecedented wave of migration toward Europe from Africa and the Middle East.
The U.N. refugee agency expressed shock at the scale of the deaths in Monday’s capsizing and renewed calls on European governments to redouble search and rescue efforts. The International Organization for Migration maintained that the situation had reached “crisis proportions.”
The Mediterranean “has emerged as the most dangerous” of four major sea routes used by the world’s refugees and migrants, taken by 219,000 people last year, said U.N. High Commissioner for Refugees Antonio Guterres.
The Italian Coast Guard rescued about 140 people off the coast of Libya on Monday and recovered nine bodies. They could see immediately from the size of the capsized smuggler’s boat that there likely had been hundreds more on board.
The rescue was made during a five-day surge in which Italian ships saved nearly 10,000 people at sea since Friday — an unprecedented rate in such a short period, said Cmdr. Filippo Marini, a coast guard spokesman.
The number is likely to grow, with summer weather encouraging even more people fleeing poverty and conflict to make the perilous crossing.
Survivors of Monday’s shipwreck reported that as many as 550 people were on board, according to aid workers.
“Of course, this is an estimate. No one who travels knows exactly the number. They don’t get a ticket that says: No. 550,” said Barbara Molinario, the U.N. High Commissioner for Refugees spokeswoman in Italy.
Accounts by survivors, mostly sub-Saharan Africans, indicate the ship capsized when men on the upper deck rushed to wave down a ship they thought to be a rescue vessel, said IOM spokesman Joel Millman in Geneva.
“Many were waving and gesticulating to get attention, and that caused the vessel to capsize, with the speculation that women and children who were below deck were drowned instantly,” Millman said.
The rescued migrants arrived Wednesday at the Italian port of Corigliano. A precise accounting of the number of dead will never be known: The search operation was called off after the recovery of nine bodies because of the depth of the sea. There will be no body count to verify survivors’ accounts, as is nearly always the case.
The UNHCR estimates 3,500 migrants died in the Mediterranean last year, up from 600 in 2013.
With few bodies recovered, many deaths are never confirmed officially. Instead, their fates are recounted by survivors and, in cases when boats are lost at sea without any rescue attempt, by relatives who report their failure to arrive in Europe. Overall, since 2000, the IOM estimates that more than 22,000 migrants have lost their lives trying to reach Europe, although there are no precise figures.
The U.N. refugee agency is compiling a list of all such incidents since 2011, but Molinario declined to disclose figures because they are just estimates.
“We take it very seriously if various families call in with the same information: ‘My relatives were on the boat with 300 people.’ When we get 10 or 15 calls with the same data, there is no reason we shouldn’t believe a boat departed on that day,” Molinario said.
Far less common are shipwrecks near shore, like the one near Lampedusa on Oct. 3, 2013, when divers recovered more than 360 bodies. About a week later, another boat sank off Malta, with about 200 dead, most never recovered.
The twin tragedies focused world outrage and prompted Italy to create a search and rescue operation to patrol the high seas, dubbed Mare Nostrum, or Our Sea. It was scrapped late last year under political pressure in the cash-strapped nation, which was spending $10 million a month on the program. In its place, Europe has responded with border patrols that often take far longer to reach distressed vessels on the high seas.
Monday’s tragedy “only demonstrates how important it is to have a robust rescue-at-sea mechanism in the central Mediterranean,” said Guterres.
Q&A: Migrant ships in the Mediterranean
Q: Why are people risking their lives to reach Europe?
A: Some are fleeing conflict or persecution, and others are looking for a way out of poverty. They come from countries such as Eritrea, Niger, Syria, Iraq and Somalia. Many claim to be Syrian to improve their chances of staying. Right now, the weather is good, so smugglers are bringing over more people willing to spend thousands of euro apiece to risk their lives on poorly maintained, crowded boats.
Q: How big is the problem?
A: Almost 280,000 people, some refugees escaping conflict, entered the EU illegally last year, a 138 percent increase over 2013. The International Organization for Migration estimates that at least 3,279 died in the Mediterranean in 2014.
Q: How do they get to Europe?
A: The main route is through conflict-torn Libya, where there are no effective border controls and smugglers are operating with near-impunity. They have developed a well-oiled operation of acquiring boats and sending the migrants off with a satellite phone to make a call to Italian or Maltese authorities to come to their rescue once they’re at sea.
