Oregon Sen. Jeff Merkley says tent encampments holding migrant children for immigration violations along the U.S.-Mexico border need to be shut down.

The Democratic senator's comments come Saturday after visiting a tent encampment in Tornillo, Texas, 17 miles east of El Paso, where about 2,700 migrant children are being held in the custody of the Department of Health and Human Services.

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"This is a child prison strategy that inflicts trauma on children," Merkley said. "It's part of the broader strategy of the Trump administration to inflict trauma on children that began with the child separation policy, and it's completely unacceptable."

Nearly half of the kids being held at the camp remain in detention despite having identified sponsors waiting to house them, according to Merkley. He says more than 2,000 of the children have been locked up for more than 20 days despite a 9th Circuit Court ruling on a 1997 federal court decision known as the Flores agreement, which set 20 days as the maximum length of time unaccompanied children could be held by the government.

Merkley's trip could foreshadow efforts by Democrats in 2019 to prioritize child treatment along the U.S. border when newly elected leaders begin work in January. Merkley says he expects investigations and hearings into the issue in the U.S. House of Representatives, where Democrats have gained a majority.

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Still, Merkley's trip to the border did not come without problems.

The senator was joined on a two-day trip by a delegation that included Sens. Mazie Hirono, D-Hawaii, and Tina Smith, D-Minnesota, along with Reps. Beto O'Rourke, D-Texas, and Judy Chu, D-California. The delegation hoped to use its presence to pressure border officials into letting the senators and representatives see the facilities in Tornillo, Karnes City and Dilley, Texas.

The delegation threatened to show up at the entrance of the Tornillo facility and "dramatize" efforts to keep them out after being initially told they could not visit on Saturday. Merkley made headlines in June for doing just that; he filmed his encounter with immigration authorities who denied him access to a detention center in McAllen, Texas.

"Congress can't exercise oversight if you can't visit a place," Merkley said. "And you can't really know what's going on if you can't talk to people who are there."

The delegation planned to talk with children about their experiences at Tornillo. They were not allowed to, according to Merkley.

"There's so much secrecy around this child prison system," he said. "All we could do was say hello and hear a few interactions asking, 'Where did you come from?' as they passed by."

The delegation's trip also came the same week media outlets reported that a 7-year-old Guatemalan girl who crossed the border earlier this month died of dehydration and shock while in Border Patrol custody.