WASHINGTON - US Customs and Border Protection announced medical checks on all children in its custody following the death of an eight-year-old Guatemalan migrant - the second child fatality in US detention this month.

Guatemala called for an investigation into the boy's death and some US lawmakers angrily denounced the Trump administration's immigration policy.

The boy, identified by Texas congressman Joaquin Castro as Felipe Alonzo Gomez, and his father were in CBP custody on Monday when a Border Patrol agent noticed the child showing signs of illness, CBP said in a statement. The father and son were taken to the Gerald Champion Regional Medical Center in Alamogordo, New Mexico, where the boy was diagnosed with a common cold and fever, and eventually released by hospital staff.

But later that evening, the boy began vomiting and was transferred back to the hospital. He died there early on Tuesday, CBP said, adding that the official cause of death was not known.

The agency said it would release more details "as available and appropriate".

Late on Tuesday, commissioner Kevin K. McAleenan announced the agency was "conducting secondary medical checks upon all children in CBP care and custody", and "reviewing its policies with particular focus upon care and custody of children under 10".

"This is a tragic loss. On behalf of US Customs and Border Protection, our deepest sympathies go out to the family," he added.

McAleenan said the CBP was considering seeking medical support from other government agencies, among them the US Coast Guard and the Department of Defense.

Guatemala called on US authorities to conduct a "clear" investigation of the death, adding that "medical reports have been requested ... to clarify the cause of death of the child".

The news of the boy's death triggered outrage among lawmakers.

"The Administration's policy of turning people away from legal ports of entry... is putting families and children in great danger," Castro, chairman elect of the Congressional Hispanic Caucus, said in a statement.

The boy's death came on the same day that Jakelin Caal, a Guatemalan girl who died in US custody under similar circumstances earlier this month, was buried.

Her body was repatriated on Sunday and after a long journey reached San Antonio Secortez, the remote village where her family - members of the indigenous Q'eqchi' Maya people - live without electricity and other basic services.

"This girl left home happy searching for a dream, but unfortunately died on the way," community leader Alberto Pop said in the cemetery.

Caal's Dec 8 death reignited debate in the US over immigration policy and the treatment of migrants.

US President Donald Trump has made hardline immigration policies a central plank of his presidency, drawing fire from critics who accuse him of demonizing migrants for political gain.

He is locked in a battle with Congress over funding for his planned wall along the border with Mexico, which he says will stem migration from Latin American countries plagued by gang violence and poverty.

"Heartbroken to hear of a second child's death in CBP custody," tweeted Nydia Velazquez, a Democratic congresswoman from New York.

"We must demand accountability, find answers and put an end to this Administration's hateful, dangerous anti-immigrant policies."

AFP - Reuters