A Guatemalan child detained by U.S. Customs and Border Patrol died early Tuesday at a hospital in New Mexico, the agency reported.

The unidentified child is the second border-crosser to die in government custody this month. Seven-year-old Jakelin Caal died Dec. 7 of dehydration and shock, less than a day after she was apprehended by border agents.

In the second case, an agent noticed Monday that the child had become ill. The boy and his father were taken to Gerald Champion Regional Medical Center in Alamogordo, N.M., where the boy was diagnosed with a cold, according to a CBP news release.

Later, he was found to have a fever and was held for an additional 90 minutes before he was released with prescriptions for an antibiotic and ibuprofen.

But the child became more seriously ill Monday night, when he vomited, and was taken back to the hospital. He died shortly after midnight on Christmas Day.

The cause of the child’s death is not known. An investigation into CBP actions will be conducted, the news release said.

The medical center referred calls to a spokeswoman who did not immediately respond to messages requesting comment.

The border agency has not yet said when the father and son entered the United States or how long they were detained, saying only in its statement that the boy had been “previously apprehended” by its agents.

Alamogordo is about 90 miles (145 kilometers) from the U.S.-Mexico border at El Paso, Texas. Ruben Garcia, director of El Paso's Annunciation House, said Tuesday that he had no reason to believe his shelter had served the family, but was waiting for further details about what happened.

A CBP spokesman declined to elaborate Tuesday, but said more details would be released shortly.

This article contains information from the Associated Press.