A Brazilian mother and nine-year-old son separated at the U.S.-Mexico border were together again Thursday after a federal judge in Chicago ordered the U.S. government to release the boy, in one of the first examples of an urgent petition for court intervention successfully reuniting parent and child.

Facing reporters together just hours after the reunion, Lidia Karine Souza and her son, Diogo, wrapped their arms around each other. Diogo frequently looked up at his mom and smiled.

Asked if she had a message for President Donald Trump about her ordeal and his zero-tolerance policy that separated hundreds of children from their parents, the mother responded through a translator, "Don't do this to the children."

Under Trump's policy, the government has begun prosecuting all migrants caught entering the country without authorization. Trump has halted his policy of taking children from their detained parents under public pressure but around 2,000 of them are still being held, with many families saying they've not known how to locate them.

Jesse Bless, an attorney for Souza and her son who stood with them at their news conference, described the ruling by U.S. District Judge Manish Shah as unique, adding he hoped it would "open the door" for others to do the same and help hasten a resolution to the crisis.

When asked about advice she'd give to others facing similar challenges in getting their kids back, Souza said: "Don't give up, be persistent."

She turned herself and her son in to U.S. authorities at the Texas border and requested asylum, arguing her life was in danger in her native Brazil. She hasn't said how. U.S. officials detained her in Texas and took her son on May 30 without telling her where he would be.

When she was released June 9, she said, another detained mother who had also been separated from her child told her to check a Chicago shelter, and there she found Diogo. They were allowed no more than weekly 20-minute phone calls, in which he begged her to get them reunited.

Shah, the son of immigrants from India, mulled his decision for just four hours before ordering the government to immediately turn the boy over to his mom. Diogo had spent four weeks at the government-contracted shelter.

The boy appeared relaxed fielding questions before dozens of TV cameras and reporters at their lawyers' office in a Chicago high-rise building. But he said the days and weeks after he was separated from his mom were difficult.

"I cried almost every day I wasn't with my mother," he said, also speaking through a translator.

The reunion occurred as the White House is under increasing pressure to bring families back together after another judge's order this week ordered federal officials to do so in 30 days for many parents and children. Critics say the government has no clear plan to reunite them.

White House spokeswoman Lindsay Walters told reporters on Air Force One that various federal agencies "are continuing to work through ensuring that remaining children are reunified with their parents." When asked if the Health and Human Services Department —the agency that's in charge of reuniting families— will be able to comply with the 30-day deadline, she called on Congress to reform the nation's immigration system.

Police arrested nearly 600 people Thursday in Washington, D.C., after hundreds of loudly chanting women demonstrated inside a Senate office building against Trump's immigration policy. Among those arrested was Rep. Pramila Jayapal, the Democrat from Washington state said on Twitter.

Meanwhile, first lady Melania Trump spent time with children at a complex in Phoenix where dozens of migrant children separated from their parents at the border are being held.

After her release from an immigrant detention facility in Texas early this month, Souza lived with relatives outside Boston, where she planned to return with Diogo.

Shah, who heard arguments Thursday morning, wrote in his ruling: "Continued separation of ... [the] nine year-old child, and Souza irreparably harms them both."

The fitness of the mother in this case isn't questioned, Shah said, so dragging out processing "only serves to interfere in the family's integrity with little to no benefit to the government's interests."

During much of his time at the shelter, Souza's son was alone in a room, quarantined with chickenpox. He spent his ninth birthday on Monday without his mom.

Souza has said Diogo would beg her through tears to do everything in her power to get him back to her. The 27-year-old woman searched for weeks to find Diogo after their separation in May. When she was released, she filled out nearly 40 pages of documents that U.S. officials told her were required to regain custody.

Then they told her that the rules had changed and that she needed any family members living with her in the United States to be fingerprinted and still more documents.

Shah wrote in his three-page ruling that he understood that the paperwork, filings and forms normally required before the government can release a child in its custody are intended to ensure the child's well-being. But, he said, "the government's interests in completing certain procedures to be sure that (Souza's child) is placed in a safe environment and in managing the response to ongoing class litigation do not outweigh the family's interest in reuniting."

Government attorney Craig Oswald told Shah that U.S. officials have been "raked over the coals ... before" for not being thorough about such background checks, which he said are meant to ensure a child's safety.

Souza was seeking safety by coming to the U.S. but she told The Associated Press in an interview on Wednesday that "this ... is a nightmare." On Thursday, though, she told reporters the court ruling restored her faith that the welfare of children was important to many Americans.

For days and weeks now, some of the hundreds of parents separated from their children at the Mexican border by the Trump administration have been battling one of the world's most complex immigration systems to find their youngsters and get them back.

For many, it has been a lopsided battle, and a frustrating and heartbreaking one. Most do not speak English. Many know nothing about their children's whereabouts. And some say their calls to the government's 1-800 information hotline have gone unanswered.

Children have been sent to shelters all over the United States, thousands of miles from the border. And perhaps hundreds of parents have already been deported from the U.S. without their children.

After tracking down her son, Souza was told the soonest he could be released would be in late July. She visited Diogo for the first time since May on Tuesday and they embraced.

She kissed him several times on the head and face, then grabbed his cheeks gently with her hands as they both cried.

"I missed you so much," she said in Portuguese.

Their visit lasted an hour. Then he returned to U.S. government custody.

On Thursday, Souza said she had reason to worry her son wasn't eating well and could lose weight.

"But he's good," she said. "At first, he said the food was really bad — but it doesn't look like it."