An 8-year-old boy from Guatemala died in United States custody early Christmas Day, the second death of a child in detention at the southwest border in less than three weeks, raising questions about the ability of federal agents running the crowded migrant border facilities to care for those who fall ill.

The number of migrant families and unaccompanied minors journeying over land to the United States has swelled in the last year. Migrants are usually transferred to facilities designed to hold adults after being arrested by federal authorities while attempting to enter the country illegally or after being processed at a port of entry.

The boy, who has not been named, died just after midnight on Tuesday at a hospital in Alamogordo, N.M., where he and his father had been taken after a Border Patrol agent saw what appeared to be signs of sickness, according to United States Customs and Border Protection. His death follows that of a 7-year-old girl from the same country while also in the custody of the Border Patrol.

Much about the circumstances of the boy’s death remains unknown. It is not clear whether his condition was attributable to the care he received in the facilities, the result of an arduous journey, or some combination of the two.