Investigators have discovered “serious irregularities” at the prison where financier Jeffrey Epstein took his own life over the weekend, the US attorney general has said.

William Barr said he and his team were angry to learn that staff at the Metropolitan Correctional Centre in New York had "failed to adequately secure this prisoner".

Mr Epstein, who was facing a string of sex trafficking and conspiracy charges, died on Saturday in what prison officials said was an apparent suicide.

His death has cut short a criminal prosecution that could have pulled back the curtain on the billionaire’s life, including his connections to celebrities and presidents.

Prosecutors have vowed to continue investigating, with Mr Barr warning that any co-conspirators “should not rest easy”.

Speaking at a press conference in New Orleans, Mr Barr said: “I was appalled, and indeed the whole department was frankly angry, to learn of the MCC’s failure to adequately secure this prisoner.”

He added that the Department of Justice was “now learning of serious irregularities at this facility that are deeply concerning and demand a thorough investigation”.

The Attorney General said the case was important to the DoJ, the FBI and the complainers in the case “who had the courage to come forward and deserve the opportunity to confront the accused in the courtroom”.

He went on: “We will get to the bottom of what happened and there will be accountability.

“Let me assure you, this case will continue against anyone who was complicit with Epstein.

“The victims deserve justice and they will get it.”

Mr Barr did not provide specific details but said investigations by the FBI and the Justice Department inspectors general are continuing.

His comments came after sources at the prison claimed the unit was facing staffing shortages at the time of Mr Epstein’s death.

Mr Epstein, 66, had been denied bail and faced up to 45 years behind bars on federal sex trafficking and conspiracy charges. He had pleaded not guilty and was awaiting trial.

The manner in which he died remains a mystery, but guards on Epstein's unit were working extreme overtime shifts to make up for staffing shortages, a person familiar with the jail's operations said.

The source said the MCC's Special Housing Unit was staffed with one guard working a fifth straight day of overtime and another who was working mandatory overtime.

Epstein had been placed on suicide watch after he was found a little over two weeks ago with bruising on his neck, according to the person familiar with the matter.

But he was taken off the watch at the end of July and therefore was not on it at the time of his death.

Epstein's removal from suicide watch would have been approved by both the warden of the jail and the facility's chief psychologist, said Jack Donson, a former prison official who worked for the Bureau of Prisons for more than two decades.

His death has prompted an outpouring of conspiracy theories and misinformation online.

Many rumours have centres on what politicians may have known about Mr Epstein’s alleged crimes and whether someone may have wanted him dead.

While there is nothing to suggest this was the case, the hashtag #EpsteinMurder began trending worldwide on Saturday.

President Trump even shared a tweet stating that “Epstein had information on Bill Clinton and now he’s dead”.

Last week, more than 2,000 pages of documents were released, related to a since-settled lawsuit against Epstein's ex-girlfriend by Virginia Giuffre, one of Epstein's accusers.

The records contain graphic allegations against Epstein, as well as the transcript of a 2016 deposition of Epstein in which he repeatedly refused to answer questions to avoid incriminating himself.

Epstein's July 6 arrest drew national attention, particularly focusing on a deal that allowed him to plead guilty in 2008 to soliciting a minor for prostitution in Florida and avoid more serious federal charges.

His lawyers maintained that the new charges in New York were covered by the 2008 plea deal and that Epstein had not had any illicit contact with underage girls since serving his 13-month sentence in Florida.

The federal investigation into the allegations remains ongoing, US Attorney Geoffrey Berman said. He noted that the indictment against Epstein includes a conspiracy charge, suggesting others could face charges in the case.

Mr Epstein was well known for his famous circle of friends and associates, including US President Donald Trump, Prince Andrew and actor Kevin Spacey.

Meanwhile, questions are also being asked of Mr Epstein’s former girlfriend Ghislaine Maxwell and what role she might have played in procuring underage girls for the financier.

Ms Giuffre accused Ms Maxwell, daughter of late newspaper tycoon Robert Maxwell, of recruiting her as a masseuse for Mr Epstein at the age of 15.

She sued Ms Maxwell in 2015 for defamation – a case which has since been settled – after the media heiress accused her of being a liar.

Reports also suggest that Ms Maxwell, who denies any wrongdoing, continued to work with MR Epstein long after their romantic relationship ended.

In court documents, former employees at the Epstein mansion in Palm Beach describe her as the house manager who oversaw staff, handled finances and served as social co-ordinator.