HOUSTON (AP) — Juan de León Gutiérrez told his mother he was calling from a warehouse in Mexico, hidden by a human smuggler who had been paid to take the teenager into the United States.

“He told me he had something of a headache, perhaps because he was hungry and had not been able to sleep,” said his mother, Tránsito Gutiérrez de León.

The 16-year-old died on April 30 after officials at a Texas youth detention facility noticed he was sick, becoming the third Guatemalan child to die in U.S. custody since December.

The death has heightened scrutiny of the U.S. government’s ability to adequately care for the surge in migrant families and children crossing the border in recent months. The two earlier deaths — of children aged 7 and 8 — had already prompted border authorities to change practices to ensure that sick immigrants were getting the proper medical care.

Almost a week after the teenager’s death, the U.S. Department of Health and Human Services has not said why he was first taken to the hospital and released, only to return one day later. Evelyn Stauffer, an HHS spokeswoman, declined to provide more information Wednesday.

Juan had a rare condition known as Pott’s puffy tumor, according to the Nueces County medical examiner in Corpus Christi, citing information from a children’s hospital in Corpus Christi, where he was in intensive care for several days before his death.

Despite the name, the condition is not the same as a cancerous tumor. The name refers to the swelling that occurs on a patient’s forehead caused by an infection in the frontal bone. The condition is rare, and while usually treatable with antibiotics, it can require surgery.

Two pediatricians told The Associated Press that the condition is often caused by severe sinus infection, which can lead to bacteria building up in a person’s head and spreading. An unchecked head injury can also lead to bacteria spreading. Headaches are a common symptom as well as vomiting and fever.

It’s unclear when Juan first got sick. Tránsito Gutiérrez de León said this week that her son had never had any serious illnesses beyond colds or an occasional cough, which were treated “with remedies from the land, the only thing we have.”

Gutiérrez said when her son called her, using the smuggler’s cellphone, he told her he had “a kind of headache.” She said he told her he hadn’t eaten anything or had water that day. She doesn’t remember what date the conversation occurred.

“The last time we talked he told me he hoped God would help us with salt or corn, or perhaps beans for us,” she said.

Juan was from Camotán, one of the poorest, most arid parts of Guatemala in what’s known as the dry corridor, where there has been a prolonged drought for nearly two years.

According to Guatemala’s foreign ministry, the teenager entered the U.S. near El Paso on April 19 and moved to a shelter in Brownsville the next day.

An official who was not authorized to disclose information about the case said Juan was taken to Casa Padre, a facility operated by the Texas nonprofit Southwest Key that holds up to 1,400 people in a converted Walmart.

U.S. Health and Human Services said in a statement last week that the teenager became “noticeably ill” on the morning of April 21, with symptoms that included fever, chills, and a headache.

He was taken to a hospital emergency department that morning and released.

When the teen’s health did not improve, Juan was taken by ambulance to another hospital emergency room. He was transferred later that day to Driscoll Children’s Hospital in Corpus Christi, roughly 160 miles (257 kilometers) from Brownsville.

The Guatemalan foreign ministry said Juan had undergone surgery to “stabilize the pressure inside the area of his head” and received “intensive therapy with 24-hour monitoring.”

Dr. Katherine Ratzan Peeler, a pediatrician affiliated with the advocacy group Physicians for Human Rights, called on the U.S. government to release more information about how it handled Juan’s case.

Releasing the teen at first from the emergency room may not have been a mistake depending on his symptoms at the time and what treatment or follow-up steps he was given, Peeler said. Without further information, it would be impossible to evaluate whether his caregivers missed warning signs.

“That happens even in the best children’s hospitals in the country, where we send someone home and they come back the next day and they have something pretty bad where you couldn’t just quite tell the first time around,” she said.

Dr. Mobeen Rathore, a pediatrician based in Jacksonville, Florida, and spokesperson for American Academy of Pediatrics, said Juan’s death was further evidence that detaining immigrant children was a health risk under any circumstances.

“If a child was in a home and not in a detention center with 1,400 kids … there would be more attention paid to this, whether by a parent or a guardian or whoever,” Rathore said.

The Guatemalan consulate in McAllen, Texas, said it is preparing to return Juan’s body to his home. An official at the consulate said the Guatemalan government would cover all funeral costs involved.

Tránsito Gutiérrez de León said her family had no money, not even to take the bus to the capital of Guatemala City where an airplane carrying his body will likely arrive.

Pérez reported from Guatemala City.

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