Oregon Sen. Jeff Merkley has, for a third time, returned to the southern border -- this time to investigate the Christmas Eve death of an 8-year-old Guatemalan child being held by U.S. officials.

Merkley was accompanied by members of the Congressional Hispanic Caucus. They were scheduled to visit the remote Alamogordo Border Patrol Station where Felipe Alonzo-Gomez was staying prior to his death.

The boy and his father were apprehended by border patrol agents on Dec. 18 about 3 miles west of the Paso Del Norte port of entry in El Paso, Texas. They were moved to Alamogordo, 80 miles away, several days later.

According to federal records and media accounts, a federal agent noticed that the child was coughing and appeared to be ill about 9 a.m. Dec. 24. Officials diagnosed him with a cold and gave him Tylenol. But Alonzo-Gomez’ condition worsened during the course of the day and by evening was feverish and vomiting.

With no doctor or EMT on duty, federal agents transferred him to the Gerald Champion Regional Medical Center. Alonzo-Gomez lost consciousness during the trip to the hospital and could not be revived. He was the second migrant child to die in federal custody in recent months.

The political battle over immigration is more intense than ever. President Donald Trump has insisted Congress fund a $5.7 billion border wall and has scheduled a prime-time address Tuesday to make his case with the public.

In one of many Tweets on the subject, Trump said a wall would reduce crime and save the country big money. "99% of our illegal Border crossings will end, crime in our Country will go way down and we will save billions of dollars a year," the President tweeted.

Congress has been unwilling to fund Trump’s wall, and the resulting stalemate has led to a government shutdown now entering its 17th day.

“The poor treatment of children seems to be part of an ongoing Trump war on migrant children,” Merkley said Monday. An estimated 15,000 children were held in what Merkley called “internment camps” near the U.S.-Mexico border.

Merkley first traveled to the border last June where he was denied entry to a Texas facility housing migrant children who’d been separated from their parents while trying to cross into the country. The resulting publicity helped ignite a national controversy over the Trump administration’s family separation policies.