A United Nations human rights expert called on U.S. authorities on Monday to conduct a full and independent investigation into the death of a seven-year-old Guatemalan migrant girl in U.S. custody and to stop detaining children.

Felipe González Morales, U.N. special rapporteur on the human rights of migrants, also said the family of Jakelin Caal, from the Mayan indigenous community, should be given access to legal representation in the proceedings in a language they understand.

"Redress to her family should be provided and if any officials are found responsible they should be held accountable," he said in a statement.

"The government should also address failings within the immigration system, and specifically within the US Customs and Border Patrol agency, to prevent similar situations."

Caal and her father Nery were in a group of more than 160 migrants who handed themselves in to U.S. border agents in New Mexico on Dec. 6. Jakelin developed a high fever while in the custody of U.S. Customs and Border Protection and died two days later at a hospital in El Paso, Texas.

"The U.S. authorities must ensure that an in-depth, independent investigation of the death of Jakelin Ameí Caal is conducted," González Morales, who is a Chilean professor of international law, said in the statement.

U.S. officials have said the U.S. Department of Homeland Security's internal watchdog will investigate the girl's death.

Initial news reports said Caal died of dehydration and exhaustion. Later U.S. officials said she had suffered cardiac arrest, brain swelling and liver failure.

Gonzalez Morales called on the Trump administration to halt the detention of children, unaccompanied or with their families, based on their migratory status, and to seek alternatives.

"As repeatedly stated by a series of UN human rights bodies, detention of children based on their migratory status is a violation of international law," he said.

Detention is detrimental to a child's well-being, produces long-term severe adverse impacts and exacerbates the trauma that many suffer along their migration journeys, he said.

The U.S. authorities’ treatment of migrants and "the public discourse about immigration in the US", were of great concern, Gonzalez Morales said.

His two requests to carry out an official visit to the United States to obtain first-hand information had not received a reply, he said.