U.S. Customs and Border Protection has confirmed a 45-year-old Mexican national died Monday morning while in their custody.
The individual has not yet been identified.
In a statement, CBP says border patrol agents apprehended the Mexican national for illegal re-entry on Feb. 2.
The Roma Police Department encountered the individual near a port of entry and requested medical attention. The migrant was then transported to a medical center in Mission.
Medical officials cleared the individual to travel and returned the migrant to the custody of the Rio Grande City Border Patrol Station.
The next day, medical attention was requested again. The migrant remained under medical care in McAllen until Monday, when the individual died.
The migrant was initially diagnosed with cirrhosis of the liver and congestive heart failure. The official cause of death is still unknown.
CBP is reviewing the incident, and the Mexican government was notified.
The incident follows the death of two migrant children in the custody of CBP within the last three months.