The two staff members in the special housing unit where Mr. Epstein was held — 9 South — are accused of falsely recording in a log that they had checked on Mr. Epstein every 30 minutes, as was required. But Mr. Epstein, who had been removed from suicide watch after apparently trying to kill himself on July 23, had not been checked on for about three hours, several law enforcement and prison officials with knowledge of the matter have said.

The subpoenas seek testimony from the jail employees and are part of an inquiry being conducted by the F.B.I., prosecutors with the Southern District of New York and investigators from the New York office of the Department of Justice’s inspector general, said a person with knowledge of the investigation, who asked to remain anonymous because he was not authorized to speak on the matter. It was unclear whether the subpoenas also sought records or other materials.

The New York City medical examiner determined that Mr. Epstein’s Aug. 10 death was a suicide by hanging. Still, that has not quashed unfounded conspiracy theories that claim other people may have played a role in silencing Mr. Epstein, whose social circle included celebrities, academics and powerful politicians.

Image Jeffrey Epstein was arrested in July and charged with federal sex trafficking. Credit... New York State Sex Offender Registry, via Associated Press

A decade ago, Mr. Epstein served 13 months in a Florida jail and registered as a sex offender after pleading guilty to state prostitution charges under a highly criticized agreement that, at the time, shielded him from federal prosecution.

He was arrested in July by F.B.I. agents and New York police detectives at Teterboro Airport and charged with federal sex trafficking following renewed interest in his case.

The Justice Department has announced high-level staffing changes since Mr. Epstein’s suicide.

The acting director of the Bureau of Prisons, Hugh Hurwitz, was reassigned on Monday, and the warden of the Manhattan jail, Lamine N’Diaye, was transferred to an office in Philadelphia.