US Attorney General William Barr has branded the jail cell death of paedophile Jeffrey Epstein "a perfect storm of screw-ups".
He said the multi-millionaire's suicide - which came as he awaited trial on sex trafficking charges - was due to a "series" of shocking mistakes.
The shamed paedophile's death and surfed the internet, a court has already heard.
Barr told the AP he had personally reviewed CCTV footage that confirmed nobody entered the area were Epstein was being detained on the night he died.
"I can understand people....whose minds went to sort of the worst-case scenario because it was a perfect storm of screw-ups," he said.
Epstein was placed on suicide watch after he was found on 23 July on his cell floor with evidence of bruising on his neck Metropolitan Correctional Center in downtown New York City
He was taken off suicide watch about a week before his death, though kept on a heightened watch that required him to have a cellmate.
But his cellmate was transferred on 9 August to another prison a day before Epstein's death, which a medical examiner later ruled to be suicide by hanging.
Mr Barr said: "I think it was important to have a roommate in there with him and we're looking into why that wasn't done, and I think every indication is that was a screw-up.
"The systems to assure that was done were not followed."
On Tuesday, the two prison guards pleaded not guilty to charges they falsely certified to having conducted inmate counts during Epstein's final hours, and to a conspiracy charge.
Who was Jeffrey Epstein and what was he accused of?
Jeffrey Epstein was a US financier who was convicted of soliciting an underage girl for prostitution in 2008.
He was arrested on July 6, 2019 for sex trafficking minors in Florida and New York.
Epstein was arrested on July 6, 2019 on sex trafficking charges.
Court documents allege that at least 40 underage girls were brought to Epstein’s mansion for sexual encounters.
He was arrested at Teterboro Airport in New Jersey.
FBI agents are also said to have broken down the door to his Manhattan townhouse.
He pleaded not guilty to child sex trafficking charges in New York and could have faced 45 years in prison if found guilty.
On July 18, a federal judge said that the disgraced financier presented a "danger to the community" and must stay in one of New York's toughest prisons while he awaited trial over the sex trafficking accusations.
The shamed financier was locked up amid fears he would flee the country.
Prosecutors said Noel and Thomas, the only correctional officers on duty in Epstein's unit, appeared to have fallen asleep for two hours during their shift.
Noel spent some of her waking hours surfing the internet for furniture sales and benefit websites, they said, while Thomas looked up websites for motorcycle sales and sports news.
The officers are suspected of failing to check on him every half-hour - as required - and then fabricating log entries to claim they had.
Prosecutors had offered the guards a plea bargain, but it has ben revealed they declined the deal.
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The defendants were the first to be criminally charged in connection with Epstein's death, which embarrassed federal officials because the case had an unusually high profile.
Both jailhouse guards were working overtime because of staffing shortages when Epstein was found, it has been reported.
The officers have been on leave while the FBI and Justice Department investigate the circumstances surrounding Epstein's hanging.