The boy was in US custody hospital for several weeks after crossing the US to his mother, the Post reported, citing Guatemala Consul Tekandi Paniagua and another source.
CNN reaches the Department of Homeland Security and the Consulate of Guatemala in Del Rio, Texas, but has yet to receive a response.
The boy will be the fourth child of Guatemala from December to die after a stressed anxiety.
The first two deaths prompted congressional hearings, and immigration authorities ordered an increase of medical checks for children in their custody.
Homeland Officers and CBP officials announce new procedures, including additional tests for all children, with a focus on children under 10.
Started by CBP its policies in December, particularly with focus on caring for children, both in use and over 24 hours of care, the agency said.