By Alastair Leithead, BBC News
The queues of refugees start to pour over the border from first thing in the morning - as they have been doing for the last month. Ninety thousand people have so far been forcibly returned to Afghanistan from Iran since 21 April, according to the United Nations High Commissioner for Refugees.
Every hour or so another bus arrives on the Iranian side, the people are unloaded, carrying the few possessions they had when they were arrested.
A policeman meets them on the Afghanistan side, and they join a long line of people waiting to pick up the few pieces of charity an aid agency has gathered for them.
They get water, biscuits and a bundle of clothes. They can also make a free phone call to relatives to let them know where they are.
Then they get a free 120km (75mile) bus trip from the border post to the city of Herat where they are left to start all over again in a country where they used to live.
In the gathered crowd waiting to tell their stories I see a young man, a tear rolling down his cheek.
"My wife and children are left there, even though I asked the authorities to let us go together," he said, a reference number scrawled on his hand in thick black ink.
"I didn't even have time to get my wages from my employer. Now that they deported me who will look after my children? If someone throws them on the street who will give them shelter? This is cruelty."
Among the lines of men was a 12-year-old boy who said he had been deported on his own.
And passions are high. An older man, emphasising his point by striking his fist into his hand, says he has lived in Iran for 28 years and now he is back in Afghanistan, he cannot even afford the bus fare to Kabul, and doubts there is any work there anyway.
"We are Muslims and they are Muslims as well, so why have they done this to us? We don't have any one to look after us."
Iran received millions of refugees during the Soviet occupation of Afghanistan and the later civil war. It has been deporting refugees for some time, but never on this scale - never so many in such a short space of time.
Josep Zapater is from the United Nations High Commissioner for Refugees, which under its remit can do little to help most of the returnees - only the vulnerable such as the old, the young and families.
While many of the single men were living in Iran illegally, almost 22,000 of those deported have been families.
"This wasn't happening last year," Mr Zapater explained. "Also there are the human rights concerns that we have seen at the border like separated families, some cases of maltreatment.
"The process definitely needs to be sorted out in a more humane manner."
An Afghan delegation visited Iran earlier this month and they returned saying the Iranian government had promised to suspend forced expulsions, but as they delivered their report hundreds more refugees continued to be deported.
And the Iranian director general of the Bureau for Aliens and Foreign Immigrant Affairs, Ahmad Hosseini, defended their decision.
"We are determined once and for all to resolve the problem of illegal immigrants in Iran and this doesn't mean only Afghans but any other nationalities who have illegal immigrants here," he said.
"The money we were supposed to spend on reconstruction for our own country has been spent on refugees. Today when we count the cost, it is $7bn a year, or $6 per Afghan every day."
In Herat the arrival of tens of thousands of unemployed men is starting to have a real impact on the city and the whole region.
Each morning they queue up for daily work, but there is little around.
"I had my passport but they just tore it up" one man said. "What kind of law is that?"
Iran is doing a great deal to help development in Afghanistan, particularly in Herat, but there are complaints so many desperate people arriving in a short time maybe undoing efforts to stabilise and assist the people.