Immigration agents have, however, detained some teenagers who are suspected of membership in gangs like MS-13, a gang rooted in Los Angeles and El Salvador that President Trump and Attorney General Jeff Sessions have repeatedly condemned. As a general matter, the Trump administration has hardened immigration enforcement across the country, lifting guidelines established under President Barack Obama that made it unlikely that any unauthorized immigrants other than recent arrivals to the country and those with serious criminal records would be deported.
Between Mr. Trump’s inauguration and early September, the number of immigration arrests rose more than 40 percent compared with the same period last year, according to data released by Immigration and Customs Enforcement.
Rosamaria’s cousin, Aurora Cantu, a United States citizen who was riding with her in the ambulance and accompanied her to the hospital, told Rosamaria’s mother and others working on the case that the agents had at first tried to persuade the family to agree to have the girl transferred to a Mexican hospital, pressing the family to sign a voluntary departure form for her. They declined to do so. The entire time Rosamaria was in surgery and then in recovery, several armed Border Patrol agents stood outside her hospital room, the family said.
Her mother, Felipa de la Cruz, 39, said in an interview that her family had moved to Texas from Nuevo Laredo, the city in Mexico just across the border from Laredo, when her daughter was still an infant, hoping to get better treatment for her cerebral palsy.
They had not been able to afford her therapies in Mexico, she said, but in Texas, Medicaid paid for her daughter’s treatment, which included home visits from therapists.
“I’m a mother. All I wanted was for her to get the surgery that she needed,” Ms. de la Cruz said. “It never crossed my mind that any of what is happening right now could happen. When you’re a mother, all you care about is your child.”
Rosamaria’s doctors have recommended that she be released to a relative because of her illness, said Alma Ruiz, a San Antonio-based lawyer who is part of a team representing the family. But the immigration agency has not yet consented to release her.
Representative Henry Cuellar, a Democrat who represents the Laredo area in Congress, called on Wednesday for the girl to be released back to her family.
“I understand that C.B.P. has a tremendous duty to protect our nation,” he said in a statement, referring to Customs and Border Protection, “but we should be devoting our resources and focus on bigger threats.”
A spokesman for the agency, which oversees the Border Patrol, did not immediately respond to a request for comment on Wednesday night.
“The fact that they spent so much time and resources to follow this girl, to treat her like she was the highest-priority criminal that ever walked on this earth — the way they’re treating her is just beyond what a 10-year-old special needs child should be treated,” said Priscila Martinez, an immigration activist at the Workers Defense Action Fund, which is helping to plan rallies for Rosamaria in Laredo and Corpus Christi.
Rosamaria’s case is perhaps the most extreme example in recent memory of a dilemma that stalks unauthorized immigrants who live in the Rio Grande Valley, south of the Border Patrol checkpoints: Getting specialized medical care often requires going to doctors and hospitals farther north, but crossing the checkpoints could mean detention and deportation.
That, Ms. Martinez said, is why Rosamaria’s parents were absent from her side when she was rushed north to Corpus Christi, leaving her cousin, Ms. Cantu, to accompany her to the hospital.
