(CNN) The suicide of Jeffrey Epstein is bringing attention to what employees say is a broader problem at short-staffed budget-constrained federal prisons where employees who aren't prison guards are doing guard duty and overtime shifts regularly.

Attorney General William Barr said Monday that "serious irregularities" were found at the Metropolitan Correctional Center in New York, long thought to be a well-run facility that has been used to house high-profile prisoners who require highly secure conditions.

In the case of Epstein, at least one of the two employees on duty at the time was not part of the regular detention workforce but was filling in as a guard, according to a person briefed on the matter. The person's regular position is not publicly known.

Budget cuts and hiring freezes first put in place at the beginning of the Trump administration have taken a toll at law enforcement agencies including the federal Bureau of Prisons, employees say.

After years of complaints, Barr lifted the hiring freeze in April.

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