U.S. Customs and Border Protection says a 9-year-old migrant child died at a hospital in Mesa after falling ill while crossing the U.S.-Mexico border. 

CBP says the incident began the night of June 15. Border Patrol agents received a 911 call from the Santa Cruz County Sheriff's Office, which provided approximate GPS coordinates about a female migrant and her two children.

The mother told them one of her children was experiencing seizures.

Agents and Tubac Fire Department personnel took the child to a nearby hospital and airlifted him to another facility in Mesa the next afternoon. The agency says he was placed on life support with multi-organ failure there and died the next evening.

An agency spokesperson said the mother and her other child have been released from custody but did not provide more information.

The Maricopa County Medical Examiner has declined to do an autopsy, according to CBP.

The office didn’t immediately respond to questions Friday about why.