Oliver de Ros/ASSOCIATED PRESS Elvira Choc grieves as she attends a memorial service Monday for her 7-year-old granddaughter, Jakelin Caal Maquin, in San Antonio Secortez, Guatemala. The body of the girl who died in U.S. Border Patrol custody was handed over to family members in her native country for a last goodbye.

A United Nations expert on the human rights of migrants is calling for a full investigation into the death of 7-year-old Jakelin Caal Maquin, a Guatemalan migrant who survived a 2,000-mile journey to the states but died in the custody of U.S. Customs and Border Protection in less than 48 hours.

Felipe González Morales, elected as the U.N.’s special rapporteur on the human rights of migrants last year, demanded in a news release Monday that U.S. authorities “ensure that an in-depth, independent investigation” take place.

“Access to justice for her relatives should be granted, including but not limited to having legal representation in the proceedings in a language they understand well,” he said.

A full investigation would also include “redress to her family” if U.S. officials are found to be at fault and would require that officials “address failings within the immigration system” to prevent more incidents like it.

Maquin fled northern Guatemala with her father in a group of 163 migrants, according to the Department of Homeland Security. She died of shock and dehydration roughly 24 hours after being brought to a Texas hospital, The Washington Post first reported. Her identity was revealed earlier this month, and on Sunday her body was repatriated by plane from Laredo, Texas, to the Guatemalan community of Raxruha, where she was from, according to CNN.

Department of Homeland Security Secretary Kirstjen Nielsen drew fire for blaming the girl’s family for her death, saying on “Fox & Friends” that “this family chose to cross illegally.”

The U.N., meanwhile, didn’t mince words in its condemnation of the U.S. policies that led to the child’s detention in the first place.

“As repeatedly stated by a series of U.N. human rights bodies, detention of children based on their migratory status is a violation of international law,” González Morales said.

He said he has twice asked U.S. officials for permission to come visit and investigate the incident himself but hasn’t received a response.