ALTA, Norway (AP) — The job in the Moscow warehouse was nothing like Elyas and his brother had been promised. They loaded and unloaded trucks from 4 in the morning until 8 at night. They got two days off a year. Their backs ached.

So when the Afghan teenagers heard last fall that the border to Norway was open, they went for it. They sneaked into their manager's office at night, stole about $1,000 in cash and made the trip by plane, taxi and bicycle.

Now Elyas, 17, is in a shelter for unaccompanied minors in Alta, in the northernmost part of Norway, waiting to learn if he will be sent back. He moves lethargically, and the dark circles beneath his watery eyes make him look sad and tired.

"I can't sleep at night," Elyas says, his voice soft and brittle as he tells his story. "When I close my eyes, all the bad things come back."

Elyas, whose legal guardian in Norway asked that his last name not be published, is one of the tens of thousands of Afghan teenagers who showed up on Europe's doorstep last year, in perhaps the most unexpected and challenging aspect of the migrant crisis. In a matter of weeks last fall, Sweden alone received more than 20,000 young Afghans — equaling the number of unaccompanied minors that applied for asylum in all of Europe the year before.

"I have been in this business for a very long time, but this was the most remarkable development I have ever seen," says Anders Ryden, an Afghanistan expert at the Swedish Migration Agency.

As asylum-seekers stream into Europe, the number of unaccompanied children and teenagers among them overall is soaring. In Norway and Sweden, about one in five last year was a minor traveling alone, up from one in 10 the year before. Denmark, Finland, Germany, Austria and the Netherlands also registered higher shares of unaccompanied minors compared with 2014. Everywhere, Afghan boys led the flow — not Syrians, who make up the biggest group of adult asylum-seekers and families.

The exodus has put a new, youthful face on migration into Europe. But it has also strained Europe's capacity to receive migrants even more, because minors traveling alone are given priority in the asylum process and require attention from social services.

"We had to establish many more reception centers and bigger reception centers that didn't have any previous experience with unaccompanied minors," says Birgitte Lange, deputy director of the Norwegian Immigration Directorate.

In Norway, two-thirds of the 5,300 unaccompanied minors who sought asylum in 2015 were Afghans. They are now spread out in special shelters across the country. The Associated Press gained rare access to one of those shelters in Alta, a popular place to observe the aurora borealis, the spectacular display of dancing lights that fire up the sky in northern latitudes.

Elyas lives here in a former hostel with about 40 other boys from Afghanistan, Syria, Eritrea and other countries. Many are traumatized by years of war, oppression and abuse in their home countries, or shaken by an agonizing journey to Europe at the mercy of brutal human smugglers.

"They are bad people," Abdulkabir, a 15-year-old with a wispy mustache and thick eyebrows, says of the smugglers who took him from Afghanistan to Iran, Turkey and Bulgaria. "When we want water they say 'don't have water, go fast, fast.' When someone is sick they don't stop for him."

Other boys recount crossing the Sahara desert with little food and water. One says he thought he had a 50-50 chance of reaching Europe alive when he fled from a military training camp for teenagers in Eritrea. Another says he was captured by bandits in Libya who demanded ransom money from his family in Ethiopia. He clearly wants to talk about what happened to him, describing dates, times and other details of his journey with great precision. When the manager of the shelter suggests a break, he asks her not to interrupt him.

Back from a Norwegian class in school, the boys play video games or billiards. Some are camped in front of the TV or at a row of desktop computers, where they reach out to friends and family on social media. They cook their own food in the kitchen, a new experience for many who didn't even know how to fry an egg before they left their families.

Ann Roarsen, one of five nurses working with refugees at the Alta Health Center, says it's not uncommon for the boys to show stress symptoms, including heart palpitations, sweating, anxiety, muscle pain and difficulty sleeping, once they've settled down from their journey. Some get depressed and resort to deliberate self-harm, she says, making a cutting gesture over her arm.

"We also have youth with suicidal thoughts," Roarsen says, adding that only those with the most severe mental problems are offered psychiatric help.

How to deal with the unaccompanied minors has become one of the most heated discussions in Europe's handling of the migrant situation.

In Sweden, Europe's top destination for unaccompanied minors, not a week goes by without newly arrived teenagers being accused of stabbings, fights, vandalism or sexual assaults. Sometimes the young migrants are the targets of violence themselves, like in late January when a mob of masked hooligans vowed to "clean up" an area in downtown Stockholm.

In Alta, the situation has been relatively quiet. The boys say they are treated well by the local residents. Renate Moe, who oversees the shelter and another one for adults in Alta, says there haven't been any "big issues."

There was an incident in November, however, when two 16-year-old boys from the shelter were moved to another town after they were accused of harassing a 12-year-old Norwegian girl walking home from school. The details of what happened are unclear, but the girl was very frightened.

"Maybe it was just two boys trying to get to know the girl, we don't know," Moe said.

Analysts are still trying to figure out why the Afghan numbers soared so suddenly in the fall. Most cite a deteriorating security situation in Afghanistan, where civilian casualties of the war rose to record levels for the seventh year in a row in 2015, according to the United Nations. They say the violence, along with a drop in prices for human smuggling and the images of Syrian refugees entering Europe, combined to make Afghan families decide this was the time to send their sons abroad.

"They probably thought that you have to jump on this train before the doors close. Because most have figured out that sooner or later Europe will close up," says Ryden of the Swedish Migration Agency.

That's already happening. Several countries, including Sweden and Norway, have stepped up border controls. Amid suspicions that some who claim to be minors are older than 18, the Swedish government plans to introduce age tests in cases when there is doubt.

Elyas and his brother were among the more than 5,000 migrants who entered Norway from Russia in the second half of 2015.

They were taken to Russia, he says, by a powerful man in his village who promised them work so that they could send money to their parents. Instead, they finished each 16-hour shift dazed and exhausted. Then they slept on mattresses on the warehouse floor until the next shift started.

"They made us work like animals," Elyas says.

The brothers wanted to escape to Norway but had no money. That's when they stole the 70,000 rubles to pay for plane tickets to the Arctic city of Murmansk and a five-hour taxi ride to the Norwegian border.

They crossed the boundary on bicycles — pedestrians weren't allowed across. And they were greeted by polite Norwegian border police, so unlike the police officers they knew from Afghanistan or Russia.

Elyas says he felt "like a bird that is free."

After a brief stay in a border camp, he was transferred to the Alta shelter. Because his brother is 18, he was taken to an ordinary refugee shelter.

Under the 24-hour winter darkness of the polar night, relief at being safe gradually gave way to angst.

Elyas, whose case is still being processed by Norwegian immigration authorities, worries about being sent back to Russia, "where I'm sure they are waiting for me and my brother. When they catch us I don't know what they are going to do."

But most of all he worries about his parents. He hasn't spoken to them since he left Afghanistan. They are poor and have no phone or Internet access. The thought he doesn't want to think, but that keeps coming back, is whether they were punished for their sons' escape from the warehouse in Russia.

"I don't know if they are alive or not," Elyas says. For a moment, he looks like he's struggling not to fall apart.

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Associated Press journalists David Keyton in Alta, David Rising in Berlin, George Jahn in Vienna, Jan M. Olsen in Copenhagen, Denmark, Matti Huuhtanen in Helsinki and Mike Corder in Amsterdam contributed to this report.