MESSINA, Sicily >> The old music school is overflowing. The building is now a migrant shelter for unaccompanied minors, able to house 224 teenagers — except that it is overstuffed with 281. And it is only early April. Migrant season in Sicily is just beginning.

Ninety miles away near the ancient hilltop town of Mineo, the story is the same. At a repurposed military housing complex that is now Sicily’s biggest center for migrants, nearly 1,000 new people arrived in March. They were among the almost 10,000 migrants rescued at sea last month and brought to Italy, a fourfold increase from a year ago. Add to that tally 2,150 people rescued at sea Monday and Tuesday. Migration into Greece has dropped sharply since the new deal, and it is too soon to know if the Syrians, Iraqis and Afghans who favored that route will shift their attentions to Italy.

Either way, Italy could surpass the record 170,000 migrants who arrived in 2014, a reminder of an often-overlooked dimension of Europe’s refugee crisis. Even as last year’s stampede of Syrians through Greece and the Balkans plunged Europe into a political crisis, Italy was absorbing migrants from Gambia, Mali, Nigeria, Somalia and other sub-Saharan African countries.

“Now with the Balkan route closed, people are asking, ‘What will happen with the central Mediterranean?’” said Medea Savary, a spokeswoman in Sicily for the U.N. refugee agency. “There is never enough attention on this.”

Before last summer, Italy was the epicenter of the refugee crisis — and the rest of Europe largely ignored the problem. Tens of thousands of migrants risked their lives on dangerous journeys aboard rickety smuggler boats leaving the coasts of Libya or Egypt to reach Italy. The trip could take several days, in difficult seas, and more than 3,000 people died last year.

But then smugglers discovered routes from the Turkish coastline to Greek islands such as Lesbos and Chios. Many Syrians and Afghans who had been trying to reach Italy quickly shifted to this more convenient journey. During the final six months of last year more than 780,000 people went through Turkey into Greece, and then through the Balkans toward Germany and Sweden, until Balkan countries and others began erecting fences to block their passage.

Now Austrian leaders are concerned that as many as 300,000 migrants could arrive in Italy this year and attempt to move north. In response, the Austrian defense minister, Hans Peter Doskozil, announced this week that the country would introduce tougher border controls at the crucial Brenner Pass, the alpine crossing to Italy that is one of Europe’s most important north-south corridors.

Doskozil said the new controls would take effect June 1, and has suggested that Austria may build fencing similar to the controls the country erected along its border with Slovenia. Italian leaders have expressed serious concerns and sent a letter to the European migration commissioner asking his office to “verify with extreme urgency” whether the Austrian plans violated Europe’s Schengen agreement on open internal borders.

Beyond the negative impact on trade and shipping, tightening controls at the Brenner Pass could also bottle up migrants inside Italy.

“There is a risk that Europe will die here,” Arno Kompatscher, president of the Italian autonomous province of Alto Adige, which borders Austria, told the Italian newspaper La Repubblica this week. “The Brenner is the symbol of European unification, of 70 years of peace and social and economic well-being. If we devalue that symbol, if we return to the idea of small states, everything will change.”

Hundreds of miles to the south, in Sicily, aid workers and Italian officials are preparing for a busy summer as the warmer weather and calmer seas of springtime have arrived. The latest rescues came Tuesday, when 17 migrant ships bearing 2,150 people were intercepted at sea.

Adm. Nicola De Felice, who oversees the Italian navy’s operations in Sicily, said that for now the biggest problem was the lack of a stable government in Libya. Smugglers can operate with little impediment, even as the Islamic State controls part of the Libyan coastline, barely 300 miles across the sea from Italy.

“The situation there is very confused,” De Felice said in an interview. “That could create problems, both in lacking any controls over the migrant influx, and to the terrorist threat. We don’t know what is happening in Libya.”

Migrants who have reached Sicily describe a chaotic situation in Libya that has only worsened in recent years. Many of the migrants are sub-Saharan Africans who had been working in Libya before the country destabilized, or who are passing through to reach Europe. Many are fleeing political persecution in countries like Ivory Coast, Gambia and Mali. Or, in some cases, they are fleeing persecution for being gay.

The most striking change this year is the sharp rise in the number of unaccompanied minors. Nearly 2,700 of the 19,000 arrivals in Italy through the end of March were under 18 and traveling alone. One 17-year-old Malian, Ibrahim, who was rescued at sea Feb. 22, had gunshot wounds. He said he was shot through the arm, back and thigh as he fled a Libyan prison.

He had originally left Mali at the end of 2012, after his father decided to take a second wife and cast him out, along with his mother. Needing to earn money, Ibrahim spent two years herding goats near the Algerian border and eventually went to Libya, where the police harassed and imprisoned him. He was shot during his escape and a man who helped him insisted that he depart immediately on a smuggler boat, rather than be hospitalized.

“There are lots of other boys waiting in Libya to come here,” Ibrahim said during an interview at the center in Messina. “Some are working jobs there so they can come here. I want to stay here for my future. Italy saved my life. I can’t go anywhere else.”

Aid workers say such stories are commonplace. Another minor, Karim, 17, fled his native Ivory Coast after his family became entangled in the de facto civil war there last year. “First of all, I want to feel safe,” Karim said, explaining why he came to Italy. “When I was home, I never felt safe. I want to go to school and play soccer.”

© 2016 The New York Times Company