The investigation into Jeffrey Epstein’s death has intensified, with as many as 20 correctional staffers getting slapped with grand-jury subpoenas, according to a report.

Among the jailers called on the carpet are lieutenants who were in charge of the Metropolitan Correctional Center in lower Manhattan on the night the multimillionaire pedophile committed suicide, CNN reported.

Investigators hope to recreate what happened on the night two weeks ago when Epstein was found unresponsive in his cell with one end of a bedsheet tied to his bunk bed and the other tied to his neck.

The 66-year-old financier’s death has been ruled a suicide by hanging by city officials.

The Justice Department is leading the probe, and US Attorney General William Barr said on Wednesday that the investigation was “well along,” despite some witnesses being less than cooperative.

“A number of them required having union representatives and lawyers,” he said.

“I think I’ll soon be in a position to report to Congress and the public the results.”

He also said he had seen no evidence to contradict the medical examiners’s suicide finding.

Still, investigators do have a mystery to crack: How could a high-profile inmate kill himself in a heightened security unit within a federal jail, and only 11 days after he had been taken off suicide watch?

At the time of his death, Epstein was awaiting trial on federal charges that he ran a massive underage sex-trafficking ring, keeping his lavish homes in New York and Palm Beach stocked with girls as young as 14.

On July 23, he had been found at the federal jail semiconscious and with marks around his neck in an incident that was investigated as a suicide attempt.

Since then, prison officials ordered he be placed on, then off, suicide watch.

His last home was a two-man cell in the lockup’s special housing unit, where prison officials ordered he bunk with a cellmate.

But a day before his death, on Aug. 9, that other inmate, who has not been identified, was moved out of the cell, according to The Washington Post.

Epstein was alone when he killed himself, despite no fewer than eight Bureau of Prison staffers, including managers and supervisors, knowing he had to have a cellmate, The Washington Post reported, citing law-enforcement sources.

Investigators believe at least some of those staffers knew he was alone when he died in the 24 hours leading to his death.

Epstein was also supposed to be checked by guards every 30 minutes.

But two staff members who were tasked with guarding Epstein’s unit fell asleep and failed to check on him for three hours, then falsified records to make it look like they had checked him, The New York Times reported last week.