Biden pledged to end solitary confinement. Federal prisons are increasing its use.

Four months after President Joe Biden issued an executive order to overhaul the criminal justice system, promising his administration would ensure federal prisoners are in “safe and humane” confinement and “free from prolonged segregation,” the total number of inmates being held in so-called restrictive housing has been climbing, recent data shows.

Figures from the federal Bureau of Prisons analyzed by NBC News revealed that 11,368 inmates were held in restrictive housing — informally known as solitary confinement — as of Tuesday, up 7% from 10,607 inmates on May 28, the same week as when Biden signed his executive order. It’s also up more than 11% from the first few months of the Biden administration.

The number has been increasing steadily month over month, with the vast majority of inmates held in special housing units, in which they are segregated from the general population due to safety concerns or as a form of discipline. The federal government houses more than 142,000 inmates in its custody.

“It’s very unfortunate that the numbers have only moved the wrong way,” said Rep. David Trone, D-Md., who signed onto a letter this week with 11 other Democratic members of Congress urging BOP Director Colette Peters to reduce the frequency and length of solitary confinement.

“We have a real problem,” Trone told NBC News.

The numbers come to light as Peters on Thursday faced her first Senate hearing as the bureau’s director, replacing Michael Carvajal last month. Carvajal, a Trump administration holdover, stepped down amid criticism of a crisis-filled tenure marked by agency scandals over allegations of unsafe and unsanitary conditions in prisons, staff misconduct and widespread staffing shortages.

At Thursday’s hearing of the Senate Committee on the Judiciary, the committee’s chairman, Sen. Dick Durbin, D-Ill., said there may be times when solitary confinement is necessary to ensure safety and security in prisons, but asked how the BOP will address the “abuse” of its application.

Peters, who previously led Oregon’s prison system for a decade, said the issue is a priority for her.

“This is a complex issue,” she said. “This is one I’m still getting up to speed on at the bureau. But our values match in this topic area, senator.”

Durbin was among the Democrats who wrote to Peters this week regarding restrictive housing, and suggested its use “for the briefest amount of time, and only in emergency circumstances for the purpose of de-escalation,” while providing…