MEXICO CITY -- When Emiliano, 51 years old, finally reached Mexico from his native Venezuela, he was detained by Mexico's immigration authority, known by its Spanish-language initials as INM.
Imprisoned in a crowded room, he said he and other migrants were never given medications or access to their phones, even to let family know where they were.
"When you enter that place, you lost your human rights," Emiliano, identified by only his last name to protect his identity, told Human Rights Watch, per the human rights monitor's recent report. "There were so many of us, we slept one on top of the other ... Half of us have COVID-19 symptoms. I was afraid I would die."
Emiliano's experience is one of hundreds of thousands of migrants who have overwhelmed Mexico's migration authorities. But in an eleventh-hour deal with the Biden administration, Mexican President Andrés Manuel López Obrador has agreed to an unprecedented step -- accepting non-Mexican migrants expelled by the U.S. under normal legal conditions.
"This agreement now where people of many nationalities can be expelled from the United States to Mexico is going to expose tens of thousands or hundreds of thousands of people to danger, to abuses, to violence in ways that we've seen now for years," said Tyler Mattiace, the Mexico researcher for Human Rights Watch and one of the authors of that recent report.
President Joe Biden and López Obrador, often known by his initials as AMLO, spoke Tuesday as the U.S. prepares for an influx of migrants following the end of Title 42 restrictions, a public health policy used by the Trump and Biden administrations to expel migrants nearly 2.8 million times, even before they could request asylum.
"We've gotten overwhelming cooperation from Mexico," Biden said after their hour-long call, pointing to the joint statement the U.S. and Mexico released last week announcing the new agreement.
But critics, including some U.S. lawmakers and human rights groups, say the U.S. has been shirking responsibility for enforcing immigration policy under Title 42, the Trump-era policy that authorized the rapid expulsion of migrants in a purported effort to avoid the spread of COVID-19.
"Title 42 was the latest example of the U.S. outsourcing law enforcement and migration and refugee policies not only to Mexico, but also to other countries," said Erika Guevara Rosas, Amnesty International's Americas director, adding Biden is now "taking advantage of the apparatus that was left by the Trump administration."
That outsourcing takes different forms, from pushing other countries to increase their border security and deportations to increasing visa restrictions for foreigners to creating processing centers in other countries.
But Mexico in particular has taken on unprecedented responsibility for U.S. migration policies, and with the country overwhelmed by record numbers of migrants, critics like Guevara Rosas say the results are increasingly deadly and in violation of U.S. and international law.
"The government of Mexico, including President López Obrador's administration and the previous administration from different political parties, have been complicit in the committing of human rights violations against migrants and refugees that include massive pushbacks, forcibly returning people to countries where they are in danger, and not committing to provide protection to people who are stuck at the border in these communities that are experiencing high levels of violence," she told ABC News.
After Title 42 ends Thursday, the U.S. will soon shift to new, more restrictive asylum policies, including making migrants ineligible if they enter the U.S. without permission or even fail to apply for protection in another country. For migrants from Cuba, Haiti, Nicaragua, and Venezuela, that could mean immediate expulsion to Mexico, rather that removal flights to their own countries -- a policy that started under Title 42, but Mexico has now agreed to continue.
A spokesperson for the Mexican Foreign Ministry did not respond to ABC News' questions. A Biden administration official didn't address questions about the risks to migrants in Mexico, saying only, "President Biden has led the largest expansion of legal pathways for protection in decades."
The latest example of that violence came just six weeks ago when at least 39 migrants detained by INM were killed in a fire. The doors at the facility were locked, and guards were seen on surveillance footage fleeing without opening them.
INM's chief, a close AMLO ally, was charged earlier this month for "unlawful exercise of public office," although he remains out of jail and in his role. Mexico's attorney general's office said he and another high-level official failed "to complete their obligations to monitor, protect, and provide security to people and facilities under their charge, promoting crimes committed against migrants."
But the detention center in Ciudad Juárez is not the first fire to kill detained migrants, and it's not the only one where migrants have complained of severe overcrowding and poor conditions.
Mexico detained nearly 450,000 migrants in 2022 -- an increase of 44% over the year before and the highest ever recorded -- but its roughly five-dozen detention centers have capacity for less than 7,000 people, according to federal data. That makes Mexico's migrant detention program one of the largest in the world, with monitoring groups reporting some facilities -- like the one Emiliano was detained in -- lack access to running water, electricity, or medical care.
Mexico's own National Human Rights Commission has documented similar poor conditions, especially overcrowding, as well as the detention of children in violation of Mexican law.
López Obrador has repeatedly cast himself as a friend to migrants and rhetorically defended the right to seek asylum. But under U.S. pressure, he's increasingly relied on the military to act as immigration enforcement, deploying tens of thousands of National Guard troops to help detain migrants who are in the country illegally. Those detentions, including at checkpoints across the country and through random raids and searches, were declared unconstitutional by Mexico's Supreme Court last year, particularly for targeting Black, brown, or Indigenous people.
But little has changed since that ruling, and migrants' rights advocates say INM agents continue to mistreat migrants. A 2022 Human Rights Watch report documented INM agents expelling migrants seeking asylum, pressuring would-be asylum-seekers to sign papers to accept deportation, using violence to stop migrants' movements and extorting migrants for money.
More than INM, however, most of those abuses have been carried out by criminal groups, who have trafficked, kidnapped, assaulted, extorted and killed thousands of migrants traveling through Mexico -- especially those who have been waiting at the U.S.-Mexican border for a chance to cross.
Since President Joe Biden took office, there were at least 13,480 reports of murder, torture, kidnapping, rape and other violent attacks on migrants and asylum-seekers blocked in or expelled to Mexico under Title 42, according to the human rights group Human Rights First. Their report documenting those incidents, published in December, was "just a small fraction of the true number," according to Julia Neusner, the group's research and policy associate attorney.
"Organized crime is the one that has benefited more from these policies than anyone," Guevera Rosas told ABC News.
Biden administration officials have said their rollout of additional legal pathways, their encouragement to migrants to not travel to the border, and their plans to open refugee processing centers in Latin America are all meant to undercut organized crime, including the coyotes who traffic migrants.
While migrants' rights groups welcome those pathways, they argue it shouldn't undercut migrants' rights to seek asylum in the U.S. as well -- a right that is enshrined under U.S. law, even if a migrant crosses the border illegally.
"It doesn't seem that the goal of any of these policies is to streamline asylum. It seems like the goal of these policies is to make it more complicated for people to apply for asylum," said Mattiace, adding, "It's clear that Mexico's immigration policies are centered around preventing people from reaching the U.S. border."