The Trump administration is halting some hiring at the federal Bureau of Prisons, the agency where chronic understaffing has led to long overtime shifts and the use of prison nurses, teachers, cooks and other workers to guard inmates.

The move, which coincides with President Donald Trump’s aggressive campaign to cut the cost and size of the federal government, was announced last week by the agency’s newly appointed director, William K. Marshall III. Some union officials characterized the move as a “hiring freeze,” though the agency denied that, saying some positions would continue to be filled.

The Bureau of Prisons will maintain current staffing levels at least through the end of the fiscal year, Sept. 30, Marshall wrote in an email to staff titled “Staffing and Hiring Decisions.” The agency still will work to fill critical positions, such as correctional officers and medical clinicians, and will honor job offers that currently are pending on an accelerated timeline.

The change came days after Trump ordered the Bureau of Prisons to reopen Alcatraz, the former penitentiary in San Francisco Bay that last held inmates more than six decades ago.

The facility, now a popular museum and tourist attraction, likely will cost hundreds of millions of dollars to rebuild at a time when the federal prison system is facing a $3 billion repair backlog and myriad other woes. Marshall said last week that the cash-strapped agency will conduct “an immediate assessment to determine our needs and the next steps” on Trump’s Alcatraz directive.

Since mid-March, 11 federal prison inmates have died. This month, an inmate in Miami tested positive for tuberculosis, while others were diagnosed with COVID-19. In February, a Bureau of Prisons official told Congress that more than 4,000 beds within the system — the equivalent of at least two full prisons — are unusable because of dangers such as leaking or failing roofs, mold, asbestos or lead.

In his announcement, Marshall told employees that changing the Bureau of Prisons’ hiring practices are necessary to “avoid more extreme measures” as it navigates budgetary challenges. The plan will “maintain stability and protect the livelihood of our workforce to the fullest extent possible,” he wrote.

The hiring freeze is likely to exacerbate a staffing crisis at the agency, which has more than 4,000 unfilled positions, union officials said. The administration previously eliminated some pay bonuses that were credited with retaining and attracting new staff. In one example of staffing problems, a federal jail in Brooklyn had more than 150 vacancies despite a hiring surge that increased staffing by about 20 percent. Before that, the facility was operating at about 55 percent of full staffing, according to court filings.

“We’re already severely understaffed, they took our retention pay, they have been literally stripping all the things away from us that matter,” said Aaron McGlothin, union president at the federal prison in Mendota, Calif. “Freezing an already severely understaffed agency will lead to tragic consequences; we are tired of doing more with less.”

Trump suspended hiring across many parts of the federal bureaucracy when he took office in January, but initially spared the Bureau of Prisons and other law enforcement agencies. He previously imposed a hiring freeze at the bureau during his first term, in 2017.