An immigrant teenager from Guatemala died in Texas Tuesday while in federal custody, according to the federal Office of Refugee Resettlement.

The 16-year-old’s cause of death is unknown and will be investigated by the agency, according to BuzzFeed, which first reported the story. The Brownsville Herald reported that the teenager, whose identity hasn't been publicly revealed, was transferred to ORR's custody by Immigration and Customs Enforcement on April 20 and became ill the next day while in a Brownsville shelter operated by Southwest Key.

Evelyn Stauffer, a spokesperson for the Health and Human Services Administration for Children and Families, said the teenager showed no signs of illness after first arriving to the shelter but then developed fever, chills and a headache. Shelter personnel took the teen to a hospital emergency room, which treated and released him back to the shelter later that day.

“The minor’s health did not improve after being transferred back to the shelter so on the morning of April 22, 2019 the minor was taken to another hospital emergency department via ambulance," Stauffer said in a written statement. "Later that day the minor was transferred to a children’s hospital in Texas and was treated for several days in the hospital’s intensive care unit.”

Stauffer added that the child’s brother and Guatemalan consular officials were allowed to visit the teenager while he was hospitalized.

The death marks the third time a minor has died in federal custody in less than six months.

In December, Jakelin Caal Maquin, 7, died after she and her father were apprehended with a large group of undocumented immigrants near Antelope Wells, N.M., which is in the U.S. Border Patrol's El Paso sector. About two weeks later, Felipe Alonzo-Gomez, 8, died after he was apprehended in El Paso and transferred to a nearby hospital in New Mexico after falling ill. Both children were from Guatemala.

The deaths of the children prompted Customs and Border Protection to call for health screenings of children 10 or younger.