MELILLA, Spain » It was 9 a.m., and hundreds of Moroccan women, many of them older, were already at work, bent over and straining, trying to inch up the hill to the border post here. Many had bundles as big as washing machines lashed to their backs.

Dozens of others, too afraid to go farther, waited off to the side with their packages, exhaustion and defeat on their faces. Up ahead, men in yellow baseball caps, some using their belts as whips, tried to control the surging crowds with little success.

"My children need to eat," said one of the women, Rkia Rmamda, who was watching the mayhem and sobbing. "What am I going to do? I need to work."

There is probably no more abrupt economic fault line in the world than the fences that surround Melilla and Ceuta, Spain’s enclaves on the North African coast. Here just a few rows of chain link and barbed wire separate the wealth of Europe from the despair of Africa. So faint a barrier it is, and so tempting to breach, that migrants from Africa regularly try to swarm the defense. The latest attempt was a coordinated assault by about 800 people who tried to scale the fences Friday.

But the women like Rmamda, known as "mule ladies," are among the lucky few Moroccans who live in the region immediately surrounding Melilla (pronounced meh-LEE-yah) who do not need a visa to cross the border. Over the past two decades, they have turned the privilege to their meager advantage, hauling goods like used clothing, toilet paper and small electronics into Morocco from Spain, sometimes earning as little as 3 euros per trip, sometimes as much as 10. Most make no more than 15 or 20 euros a week, or $20 to $27.

"The difference in terms of income between Spain and Morocco is between 17 to 20 times," said Josi Marma Lspez Bueno, president of Promesa, which supports economic development in Melilla. He added, "It’s the biggest difference in incomes across any border."

About 300 million euros worth of various goods (about $412 million) arrive in Melilla’s port each year, virtually all headed for Morocco and beyond. But first, women like Rmamda, will carry it on their backs – or try to roll it uphill – for about a quarter-mile so Moroccan traders can avoid import taxes. Any package hand-carried to Morocco is considered luggage and therefore duty free.

In recent months, hard times in Morocco have prompted men to hustle for these jobs, too. Young and fit, they surge ahead, blocking the women and pushing them aside, kicking up dust as they carry their own gigantic bundles or roll huge tractor tires toward the crossing point, indifferent to whoever is in the way. The more times they can get back and forth across the border during the brief and arbitrary periods it is open, the more money they will earn.

By 10 a.m. one recent day, Zahra Kechache, 65, who has carried packages for more than a decade, was having an asthma attack. Nora el-Koukhou, 39, who has five children and a husband in jail, was crying after being crushed between bales in the corridor leading to the border turnstiles. One woman was lying in a ditch wailing, blood trickling from her head.

"The men make this impossible," said Rmamda, who has four children and a blind husband to feed. "This job is so dangerous now. I’m afraid I will break an arm or a leg in there."

Not until the 1990s was there any barrier of note between Morocco and Melilla. Before that, people and goods moved back and forth easily. But membership in the European Union changed all that. Spain was expected to strengthen its border controls, and it did.

It was during those years, that the job of these women was born. Women would come to Melilla early in the morning and carry the packages back home. In the beginning, they had little competition, the bales were smaller and so was the demand for goods.

These days, the packages can weigh up to 220 pounds, though most of the women carry around 150 to 175 pounds. The border is open only four days a week, and even when they show up, they may not always get a package.

The Guardia Civil, Spain’s military police force, keeps an ambulance on hand. It is needed three or four times a month, said Juan Antonio Martin Rivera, a spokesman for the Guardia Civil here.

Spanish officials say that there is little they can do about what goes on at the border, even if it is on Spanish soil. Most days, only seven Guardia Civil officers are assigned to watch over the carriers at the crossing. Most of the crowd control is left to the men in the yellow caps, who have been hired by Moroccan merchants to keep order, Martin said.

Juan Josi Imbroda, Melilla’s chief executive, says he has offered to create a bigger border crossing to relieve the pressure, but the Moroccan government has not agreed. Right now, he said, the Moroccan government is in control, opening the borders to this activity and closing it at will, fueling the need to hurry through the turnstiles while they are open and creating dangers.

The only thing Spain could do is simply eliminate the practice, he said, which could leave the women destitute.

"This is purely a socio-economic problem," Imbroda said, one "that is not easily solved."

Requests to speak with Moroccan border officials about the conditions at the Melilla crossing went unanswered.

The Guardia Civil officers assigned to make sure there are no stampedes seem to find the savagery of the scene hard to watch. "This is not work worthy of European Union," one of them said with disgust.

The carriers begin to make their way from Morocco at dawn, lining up, sometimes for hours, for an early start when the border opens at 7 a.m. Many of the women are barely surviving. Kechache, whose husband is also blind, supports him and a daughter who still lives with them in a single room. But Kechache is seven months behind on the rent and fears eviction. The family usually eats one meal a day.

Rmamda lives in a half-finished, cinder-block house with no windows, the floors covered with thin reed rugs. The wind blows through the holes in the rusting front door. On this day, she eventually got her package through the border, she said. "It was good day," she said. "Some days, I get nothing."

Even the suggestion that one of her daughters might end up hauling packages brings tears to her eyes. "This is not a life," she said, quietly, rubbing a knee that throbs constantly. A visiting neighbor, Mohamed Gabari, 46, said he tried to carry packages once but he gave up because the loads were so heavy.

Most of women carrying goods over border do not read or write. When asked their names, they pull out their passports from hand-stitched aprons under their clothes. Mostly, all they want is better order at the border. They wish, too, that the merchants would make the bundles smaller.

Some simply hope that their luck will change.

El-Koukhou used to be a maid for a Spanish family in Melilla. The days were long, but she earned 300 euros a month, a memory that still lights up her face. "I am losing my health doing this job," she said, quietly. "I am half of who I was."

© 2014 The New York Times Company