ISLAM QALA — It's almost midday when, under a blazing sun, the first bus transporting Afghans expelled from Iran arrives.

At the border crossing of Islam Qala, in western Afghanistan and 460 miles from the capital Kabul, two metal sentry boxes are built opposite one another. Over one flaps the Iranian flag, on the other the Afghan one. A few dozen yards from there, the portrait of Iran's supreme leader, Ali Khamenei, and that of its founder, Ayatollah Khomeini, are drawn next to each other on a large billboard. The two Shia dignitaries welcome travelers who leave Afghanistan for Iran.

Ghadir, 14, is the oldest of eight children in his Afghan family. His face is tanned by the sun. His hands are already calloused from the hundreds of hours he spent on construction sites. Four days ago, he was arrested while working in Qamsar, in central Iran, as police officers sought to check his residence permit.

"I'm an illegal immigrant," he says. "A month earlier, I'd paid $400 to a smuggler who got me into Iran. Where I lived in Afghanistan, in Ghor, I couldn't find any work."

The Iranian officers sent Ghadir back home as soon as they caught him. "Look at me! I've still got my working shoes and clothes on," he says, pointing to his mud-covered sneakers and his shalwar kameez — the traditional Afghan tunic — with holes.

By the busload

Since early 2015, Iranian authorities have arrested some 20,000 Afghans every month, according to figures from the International Organization for Migration (IOM). In Islam Qala, between 30 and 45 buses arrive every day, except on Fridays, the weekly holy day in Iran as well as in Afghanistan.

As an underage worker, Ghadir falls in the so-called "vulnerable" category. As such he was taken care of by the IOM as soon as he reached Islam Qala. He will be sent to the IOM transit camp in Herat where he will stay for the night, along with other unaccompanied minors, before departing for his hometown.

Humanitarian aid for these categories of people has been extremely reduced at the Iranian border and in Herat's transit camp. But it hasn't vanished. Instead it's been displaced — to deal with deportees from Pakistan.

Since the school massacre in Peshawar, Pakistan, in December 2014, Pakistani authorities have multiplied the deportations of Afghans. "In the first quarter of 2015, deportations from Pakistan were up 250% compared to the previous year," says Matthew Graydon, public information officer at the IOM. "This new situation made us turn our focus away from the Iranian border and we've been forced to cut the budget for Islam Qala."

No exceptions

IOM workers used to locate the minors' families and always had a social worker accompanying the children home. Now, the organization pays just for the transport, not knowing where these young Afghans will end up. Things are even more complicated now that it's summer, when Iran tends to step up its deportation efforts.

Pakistan only deports adult men. But Iranian authorities make no exceptions. Ghadir, for example, is by no means the only minor to have expelled from the country. Iran even deports underage girls, whether they're alone or not, or whether their parents have been located or not.

"In 2010, we took in a 10-year-old girl who was deported from Iran on her own," says Maryam Soltani, an assistant in the IOM's Herat transit camp. "She didn't know her parents' address in Iran, nor that of her family back in Afghanistan. She's been staying at a shelter for women here in Herat ever since."

Revolving door

Even though some of those deported say they won't go back to Iran, many believe they'll try their luck again in the future. "Unemployed people in Afghanistan know they'll find a job there, despite the mistreatments they must endure," an IOM worker explains.

There are an estimated 3 to 4 million Afghans living in Iran, the vast majority of them undocumented. The few jobs available to them tend to be both difficult, such as garbage collection.

Abidullah, 28, was arrested while he was taking his family from the central Iranian city of Isfahan, where he was working as an undocumented farmer, to Shiraz, more to the south. He doesn't rule out going back to Iran. The prospect of having to pay a hefty amount of money to a smuggler doesn't scare him.

"From here, I'll go home to Kunduz," he says. "But if I don't find a job there, I'll certainly go back to Iran."