A 16-year-old boy from Guatemala apprehended at the U.S.-Mexico border died on Monday after a week in Border Patrol custody ― the fifth death of a migrant child since December.

Border Patrol agents apprehended the youth, whose identity wasn’t revealed by authorities, on May 13 near Hidalgo, Texas, according to U.S. Customs and Border Protection. Agents held him at a processing center before transferring him on Sunday to a border patrol station in Weslaco.

Officials found the boy “unresponsive” on Monday morning during a welfare check, CBP said in a statement. “The cause of death is not known at this time,” the agency said.

“The men and women of U.S. Customs and Border Protection are saddened by the tragic loss of this young man and our condolences are with his family,” John Sanders, CBP’s acting commissioner, said. “CBP is committed to the health, safety and humane treatment of those in our custody.”

The agency did not say why the youth was detained for a week but said he was “due for placement” with the Health and Human Services’ Office of Refugee Resettlement.

The boy is at least the seventh migrant to die after being detained by Border Patrol since December. Five of the deaths have been children, all of whom migrated from Guatemala, which is gripped by a hunger crisis.

Last week, a 2 1/2-year-old boy apprehended with his mother at the border died after spending several weeks in a Texas hospital. CBP noted the family was no longer in Border Patrol custody at the time of the toddler’s death.

Juan de León Gutiérrez, a 16-year-old from Guatemala, died on April 30 after he was reported sick at a Texas youth detention facility. He was later found to have a rare condition known as Pott’s puffy tumor, often caused by a severe sinus infection.

An 8-year-old Guatemalan boy, identified as Felipe Gómez Alonzo, died in U.S. custody on Dec. 24 from what officials believed to be the flu. On Dec. 8, 7-year-old Jackelin Caal Maquin from Guatemala died from dehydration and shock while in Border Patrol custody.

After the deaths in December, the Department of Homeland Security expanded medical screenings and ordered medical checks of every child in its custody.