A port-mortem examination will be performed to determine the cause of death of a seven-year-old migrant girl who suffered seizures in immigration custody on the US-Mexico border and spiked a high fever, officials said.

The girl, named by the Guatemalan foreign ministry as Jackeline Caal, was found on December 6 near Lordsburg, New Mexico, by US Border Patrol agents. She was in custody for about eight hours before she began having seizures, Customs and Border Patrol officials said.

Emergency medical technicians discovered the girl’s fever was 40.9C, and she was airlifted to a hospital in El Paso, Texas, where she died.

She appeared to be dehydrated and suffering from shock and apparently had not had anything to eat or drink in days, officials said. The results of the post-mortem could take weeks, they added.

Migrants at the US borderMigrants at the US border (Moises Castillo/AP)

US Customs and Border Protection officials said the girl had been travelling with her father, correcting an earlier statement that said she was unaccompanied.

Jackeline’s death comes as increasing numbers of children and families are making the dangerous trek north from Central America and as US immigration officials are being increasingly criticised for their treatment of migrants who arrive at the US-Mexico border.

A review of what happened in the girl’s case will take place, federal officials said.

“On behalf of the Department of Homeland Security, our sincerest condolences go out to the family of the child,” said a statement from the parent department of the Border Patrol.

“Border Patrol agents took every possible step to save the child’s life under the most trying of circumstances. As fathers and mothers, brothers and sisters, we empathise with the loss of any child.”

The death raises questions about whether border agents knew she was ill and whether she was fed anything or given anything to drink during her time in custody.

Immigration officials said hundreds of people who have been overcome by the harsh desert and sweltering conditions are saved by Border Patrol every year.

People arrested by Border Patrol agents are processed at a facility but usually spend no more than 72 hours in custody before either being transferred to Immigration and Customs Enforcement or, if the person is Mexican, quickly being deported home.

Immigration officials said Jackeline died in hospital less than 24 hours after being transported.

It is unknown what happened to her during the eight hours before she started having seizures and was flown to the hospital.

The girl was travelling with a group of 163 people, who approached agents to turn themselves in on December 6, immigration officials said.