Paniagua told the Post the boy's death remains under investigation.
Authorities are also investigating the April 30 death of Juan de Leon Gutierrez, a 16-year-old migrant from Guatemala who died after officials at a Texas youth detention facility noticed he was sick. His cause of death remained unclear Thursday.
In December, 7-year-old Jakelin Caal Maquin died of dehydration and septic shock two days after she was taken to a Border Patrol station, CNN reported. The news network reported 8-year-old Felipe Gómez Alonzo died of flu complicated by sepsis weeks later, on Christmas Eve, while he was in U.S. custody. Both children were from Guatemala.
Advocates have long questioned the Border Patrol’s ability to care for the thousands of parents and children in its custody. The agency says it’s overwhelmed by the surge of migrant families crossing the U.S.-Mexico border.
The Associated Press contributed to this report.