WASHINGTON (AP) — Democrats revealed distressing new details Friday about migrant children separated from families as four of the party's star freshmen prepared to tell a House committee about the squalid conditions they saw at migrant detention stations at the U.S.-Mexico border.

Friday's House Oversight and Reform Committee hearing was coming with partisan and internal Democratic tensions running high over President Donald Trump's hard-line immigration policies. That friction was likely to increase further after the panel's Democrats released a report on 2,648 of the children the Trump administration separated from their families last year before abandoning that policy under widespread pressure.

The report, based on data the panel demanded from federal agencies, found that 18 children under age 2 — half who were just months old — were kept from their parents up to half a year. Hundreds were held longer than previously revealed, including 25 kept over a year, and at least 30 remain apart from their parents.

The figures reflected "a deliberate, unnecessary and cruel choice by President Trump and his administration," the report said.

The four Democrats testifying Friday, including progressive firebrand Rep. Alexandria Ocasio-Cortez, D-N.Y., were among a larger group of House members who visited three Texas border stations last week . That included one in El Paso, where lawmakers said they saw women packed into stuffed cells without running water.

"It was just palpable walking into that cell, you just felt suffering and trauma and fear," Rep. Ayanna Pressley, D-Mass., said Thursday, ahead of her testimony.

Friday's hearing comes as surging numbers of families, children and other migrants entering the U.S. from Mexico have overwhelmed the government's capacity to house them adequately. The two political parties are locked in a bitter struggle over the treatment of the arrivals, whose numbers have recently surpassed 100,000 monthly, and progressive Democrats accuse moderates and party leaders of too readily compromising with Trump and Republicans on the issue.

Democrats accuse Trump of tolerating badly overcrowded and putrid holding facilities in a purposeful effort to discourage future immigrants. Trump has said many migrants who've fled Central American are "living far better" in detention centers than they were at home and has said the stations are "run beautifully," though visiting lawmakers, attorneys, journalists and the government's own inspectors have reported foul conditions.

"The situation is worse than they claim it is," Oversight panel Elijah Cummings, D-Md., said Thursday.

Cummings said his message to Trump administration officials was, "Are you going to sit there and say we should be blind to what we see?"

Ocasio-Cortez and Pressley are among four progressive freshmen who call themselves "the squad," along with Reps. Rashida Tlaib of Michigan and Ilhan Omar of Minnesota. Tlaib was also testifying Friday along with Rep. Veronica Escobar, whose West Texas district includes El Paso and hugs the boundary with Mexico.

Tlaib, Pressley and Ocasio-Cortez are members of the Oversight panel. Letting them testify, rather than simply ask questions of other witnesses, will give them far more time and attention.

The four squad members, all women of color, have tried pressuring House Speaker Nancy Pelosi, D-Calif., to demand tighter restrictions on the Trump administration's treatment of migrants. The dispute has spiraled into a fight with racial overtones , dismaying Democrats as the 2020 presidential and congressional elections approach.

Also raising political temperatures are Trump-ordered nationwide raids targeting people in the U.S. illegally expected to start this weekend, according to administration officials and immigrant activists.

In June more than 104,000 people were apprehended or turned away at the border by Customs and Border Protection agents. Though that was down 40,000 from May, it was the fourth consecutive month those numbers exceeded 100,000, a level that hadn't been reached in years.

A report last week by the Department of Homeland Security's inspector general found "serious overcrowding and prolonged detention" of children, families and single adults at border facilities in Texas' Rio Grande Valley, the sector with the highest number of apprehended migrants in the country.

The report found that hundreds of children were being held longer than the supposed 72-hour limit and faced clothing shortages and a lack of hot meals, while some adults were detained for a week in a cell so crowded they had to stand.

Congress last month approved a $4.6 billion measure with money to improve border stations and migrants' treatment. That passed only after liberal and Hispanic Democrats voted "no," complaining that Pelosi hadn't fought hard enough to add requirements for how detained migrants must be treated.

Since then, Democrats have launched a legislative offensive on the issue.

Pelosi said the House will soon work on one bill by Escobar tightening oversight of the Homeland Security Department and barring most family separations. Another by Rep. Raul Ruiz, D-Calif., would establish care standards for migrants being held.

Senate Democrats introduced their own legislation Thursday curbing family separations and setting health and treatment standards.