Now, the administration is sending more than 1,600 immigrants — including some of those parents — to federal prisons amid a lack of space in other jails. The decision brought immediate denunciation from immigrant rights activists who were already enraged over the policy of separating parents from children.
The move comes as an increasing number of families and children have been coming to the border, further straining an immigration system that's already at capacity. Despite hard-line rhetoric from the White House, more than 50,000 people were apprehended at the U.S.-Mexico border in May alone — many of them families and children — and courts, asylum officers and jails are struggling to keep up with the influx.
Historically, immigrants without serious criminal records were released from custody while they pursued asylum or refugee status. The Trump administration has moved to detain more people, including asylum seekers.
Under a new zero tolerance policy, parents who are criminally charged with illegal entering the country are separated from their children while in custody. The children are usually released to other family.
Attorney General Jeff Sessions insists the policy of separating families is necessary to deter illegal border-crossings, and authorities say the decision to send people to prisons is a temporary one amid a shortage of beds.
"If you bring a child, it is still an unlawful act," Sessions said in a speech in Montana this week. "You don't get immunity if you bring a child with you. We cannot have open borders for adults with children."
Critics noted that many of those transferred to federal prison appeared to have already been convicted of the misdemeanor of unlawful entry and sentenced to time served. "Even if you accept that draconian argument, what is completely flawed is that they've already completed the criminal prosecution," said Matt Adams, legal director of the Seattle-based Northwest Immigrant Rights Project. "What is the rationale for continuing to separate them from their children and sending them to federal prison when they are just waiting for asylum?"
As Trump has ramped up enforcement, Congress continues to have little appetite for buying additional detention space — hence the crunch. In March, Congress agreed to fund 40,520 beds in immigration detention centers, an increase of 3 percent but a far cry from the administration's roughly 40 percent surge in deportation arrests. The White House had sought money for more than 51,000 beds.
In a statement Thursday, Immigration and Customs Enforcement spokeswoman Carissa Cutrell said the agency needed to acquire more than 1,600 beds in Bureau of Prisons facilities. Those include 1,000 beds in Victorville, California and 600 more in the Seattle area, Texas, Oregon and Phoenix.
"The use of BOP facilities is intended to be a temporary measure until ICE can obtain additional long-term contracts for new detention facilities or until the surge in illegal border crossings subsides," the statement said.
It's not clear how much different the conditions for the detainees will be at the prisons. Advocates have long complained about the conditions inside traditional immigration detention facilities. But Katharina Obser, a senior policy adviser with the Women's Refugee Commission, a New York-based nonprofit, called it reckless and inappropriate to house asylum seekers in federal prisons.
"This new move is due to a self-manufactured crisis that stems directly from this administration cruelly separating families at the border and locking up parents, many of whom are lawfully seeking asylum," she said.
It's also unclear if the prisons are ready for the inmates. In a statement this week, John Kostelnik, president of American Federation of Government Employees Local 3969, which represents workers at the prison in Victorville, said staffing was a major concern and that it wasn't clear how the detainees should be handled.
In a statement Friday, the Bureau of Prisons said it will house the detainees in a manner similar to inmates awaiting trial. "The BOP has bedspace available due to the decline in the inmate population over the past several years, and will use existing staff to accomplish this mission," the statement said.
Whether it's legal to house immigration detainees who aren't facing criminal charges in federal prisons is an unsettled legal question and the practice could be challenged, Adams said. But activists are primarily concerned with waiting to see whether a judge in California will issue a nationwide injunction to stop immigration authorities from separating parents from their young children, which Adams described as a much more pressing and egregious issue.
On Wednesday, the judge said that if the policy was being carried out as described, it is "brutal, offensive, and fails to comport with traditional notions of fair play and decency." Washington state officials have also expressed alarm. Gov. Jay Inslee and Attorney General Bob Ferguson issued a letter Thursday seeking more information from the federal government after learning ICE had transferred dozens of mothers who had been separated from their children to the Federal Detention Center at SeaTac.
"The Trump Administration's new family separation policy is inflicting intentional, gratuitous, and permanent trauma on young children who have done nothing wrong and on parents who often have valid claims for refugee or asylum status," they wrote.
Associated Press reporters Elliot Spagat in San Diego and Nicholas Riccardi in Denver contributed.