An 8-year-old boy from Guatemala died in government custody early Tuesday, the second immigrant child to die in detention this month.

U.S. Customs and Border Protection said the boy, identified by the Guatemalan consul in Phoenix as Felipe Gomez Alonzo, died shortly after midnight after almost a week in custody.

The boy showed “signs of potential illness” Monday morning and was taken with his father to a hospital in Alamogordo, New Mexico, CBP said. There, he was diagnosed with a cold and a fever, prescribed amoxicillin and Ibuprofen and released Monday afternoon after being held 90 minutes for observation, the agency said.

The boy was returned to the hospital Monday evening with nausea and vomiting and died hours later, CBP said. The hospital – the Gerald Champion Regional Medical Center – declined to comment, citing privacy regulations.

“This is a tragic loss," said CBP Commissioner Kevin K. McAleenan in a statement. "On behalf of U.S. Customs and Border Protection, our deepest sympathies go out to the family."

The official cause of death is not known, and in accordance with CBP policy, the agency's Office of Professional Responsibility will conduct a review. CBP notified the Department of Homeland Security’s inspector general and the Guatemalan government.

Oscar Padilla, the Guatemalan consul in Phoenix, said the boy's father told him the two were traveling from their home in Nentón, a village about 280 miles from Guatemala City. They planned to go to Johnson City, Tennessee. The consul identified the father as 47-year-old Agustin Gomez, and said he remains in U.S. Border Patrol custody.

Border patrol apprehended the father and son on Dec. 18 for illegal entry, 3.29 miles west of the Paso Del Norte Port of Entry in El Paso, Texas. Agents detained them at that port's processing center, logging six welfare checks until Thursday when they moved them to the El Paso Border Patrol Station. There, the agency said it logged another 17 welfare checks before transferring them to Alamogordo Station on Sunday to finalize processing because of capacity levels at El Paso.

Agents did several welfare checks at Alamogordo before a processing agent noticed Gomez Alonzo's symptoms at 9 a.m. local time Monday. At all three places they were detained, CBP said it gave the father and son food and drinks, as well as showers or personal hygiene products at the last two stations.

As of Tuesday night, Border Patrol said it is doing secondary medical checks on all children in custody and reviewing its policies on detaining children under age 10. CBP is also looking to relieve capacity issues in Border Patrol stations and checkpoints in El Paso Sector.

The incoming chair of the Congressional Hispanic Caucus, Rep. Joaquin Castro, D-Texas, gave his condolences to the family and called for an investigation in a statement.

"The Administration’s policy of turning people away from legal ports of entry, otherwise known as metering, is putting families and children in great danger," Castro said. "With two deaths that we know about just in the last few weeks, Congress will continue to press the Department of Homeland Security until we get answers to all our questions.”

Alamogordo, where the boy died, is about 90 miles from the U.S.-Mexican 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 spokeswoman for U.S. Rep. Steve Pearce, R-N.M., whose district along the U.S.-Mexican border includes Alamogordo, could not be reached Tuesday.

Xochitl Torres Small, a Democrat who will represent the district starting in January, called for a thorough and transparent investigation into the children’s deaths and more medical resources along the border.

“This is inexcusable,” she said in a statement Tuesday. “Instead of immediately acting to keep children and all of us safe along our border, this administration forced a government shutdown over a wall.”

Jakelin Caal Maquin, a 7-year-old Guatemalan girl, died this month in El Paso after being apprehended by border agents.

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Jakelin and her father crossed the border in New Mexico on Dec. 6, along with 161 other migrants. They were set to travel by bus to the Lordsburg Border Patrol station in New Mexico when her father, Nery Gilberto Caal, told Border Patrol agents she was sick. She was transported to a children's hospital in El Paso where she died Dec. 8.

The White House said it had no responsibility in the "horrible, tragic" situation.

Customs and Border Protection, which did not inform Congress about Jakelin's death for days, said it would follow a list of procedures when someone dies in its custody. The procedures include notifying lawmakers within 24 hours of a death.

Rep. Lou Correa, D-Calif., expressed dismay at the death of the 8-year-old boy Tuesday afternoon. He tweeted to Secretary of Homeland Security Kirstjen Nielsen, “This is the second child in a month. What is going on at @DHSgov? Does @HouseHomeland have to start subpoenaing you to get the truth?”

Other Democrats responded with criticism of border policies, including Sen. Martin Heinrich of New Mexico.

"Heartbroken and sickened by this news," Heinrich said on Twitter. "I am urgently demanding more details, but the Trump administration must be held accountable for this child’s death and all the lives they have put in danger with their intentional chaos and disregard for human life."

Several critics said the death was especially troubling given the Christmas holiday.

"The news of another child death in CBP custody is heartbreaking, especially on Christmas," Sen. Kamala Harris, D-Calif., tweeted. "We must demand a full and thorough account of what happened to this 8-year-old boy."

"Tragic news this Christmas Day," Rep. Nanette D. Barragán, D-Calif., remarked on Twitter. "Another death of a child in CBP custody? This is unacceptable. It is not ok that children are dying, that they are separated from their parents and don’t receive proper medical screenings and treatment. Congress must act. Real oversight coming 1/3."

Contributing: Kristin Lam and The Associated Press