(Reuters) - U.S. Attorney General William Barr on Monday criticized “serious irregularities” at the federal prison where Jeffrey Epstein died in an apparent suicide, adding that the sex-trafficking investigation involving the disgraced financier would continue.

Epstein was found dead on Saturday, having apparently hanged himself in his cell at the Metropolitan Correctional Center (MCC) in lower Manhattan. The 66-year-old was arrested on July 6 and pleaded not guilty to federal charges of sex trafficking involving dozens of underage girls as young as 14.

Barr, the top U.S. law enforcement official, vowed to carry on the case against anyone who was complicit with Epstein.

“Any co-conspirators should not rest easy,” he said at an event in New Orleans.

Epstein was already a registered sex offender after pleading guilty in 2008 to Florida state charges of unlawfully paying a teenage girl for sex. Prior to his conviction, he had counted the rich and powerful, including U.S. President Donald Trump and former President Bill Clinton, among his associates.

ABC News on Monday afternoon observed federal agents, including FBI and Customs and Border Protection, at the dock and on the grounds of Little Saint James, Jeffrey Epstein’s island home in the U.S. Virgin Islands.

“There are FBI agents conducting enforcement operations in the U.S. Virgin Islands,” said FBI spokesman Guillermo Gonzalez, declining further comment.

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Barr said on Saturday that he had asked the Justice Department’s inspector general to investigate Epstein’s death.

In his remarks on Monday at the Grand Lodge Fraternal Order of Police’s National Biennial Conference, Barr said the criminal case against Epstein was personally important to him and that his death denied his victims the chance to confront Epstein in a courtroom.

“I was appalled - and indeed the whole department was - and frankly angry to learn of the MCC’s failure to adequately secure this prisoner,” Barr said. “We are now learning of serious irregularities at this facility that are deeply concerning and demand a thorough investigation.”

Barr did not say what those irregularities were. The decision by officials at the Bureau of Prisons not to keep Epstein on a suicide watch has come under scrutiny.

The facility where Epstein died is run by the federal Bureau of Prisons, a division of the U.S. Justice Department.

Even before Epstein’s death, public defenders had called the MCC conditions inhumane.

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“At the very least, out of a case that’s been nothing but tragedy, maybe this will at least shine a spotlight on a facility that has had serious problems for years and years,” David Patton, executive director of the Federal Defenders of New York, said in an interview.

Patton described MCC as an “inhumane, cramped place with inadequate staffing, particularly inadequate medical staffing or mental health staffing.”

‘A TRAGEDY TO EVERYONE’

U.S. District Judge Richard Berman, who was presiding over the case, denied Epstein’s bail request last month. A few days later, Epstein was found unconscious on the floor of his jail cell with marks on his neck, and officials investigated that incident as a possible suicide or assault, according to media reports.

“Jeffrey Epstein’s death is a tragedy to everyone involved in his case,” Berman said in a statement on Monday.

It was not clear why Epstein was taken off the suicide watch. He was in a cell by himself when his body was found.

At MCC, two jail guards are required to make separate checks on all prisoners every 30 minutes, but that procedure was not followed on the night of Epstein’s death, according to an official who was not authorized to speak on the record on the matter. In addition, guards are required to make another check every 15 minutes on prisoners who are on suicide watch.

The New York Times, citing prison and law-enforcement officials, reported that one of the two people guarding Epstein was not a full-fledged correctional officer and neither guard had checked on him for several hours before he was discovered.

The New York City medical examiner said that an autopsy had been completed on Epstein on Sunday but that a determination on the cause of death is still pending.

Epstein’s death also affects civil litigation. In a court filing on Monday, two unnamed accusers of Epstein urged a federal judge in West Palm Beach, Florida, to scrap portions of Epstein’s 2008 non-prosecution agreement with federal prosecutors there that provided immunity to his alleged co-conspirators from criminal charges.

The accusers said Epstein’s death rendered moot all possible objections to scrapping the agreement.

The filing came in a long-running lawsuit by alleged victims who said prosecutors violated their rights by failing to consult them about Epstein’s plea agreement, which was made on condition that Epstein cooperate with the Florida state prosecutors.