Court documents have revealed fresh details about the death of disgraced financier Jeffrey Epstein, as US investigators lay charges against the two prison officers responsible for guarding him.

The news comes amid growing calls from Epstein's victims for his high-profile associates to speak to the FBI about what they knew about the serial sex offender.

Here's what we know.

What are the latest charges?

Tova Noel and Michael Thomas were on duty the night Epstein killed himself in a Manhattan prison, where he was awaiting trial on sex trafficking charges.

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They were supposed to be checking in on Epstein every 30 minutes, given he had been placed on suicide watch.

Instead, prosecutors allege, they spent the night sitting at their desks (4.5 metres away from Epstein's cell) browsing the internet, walking around the common area and even falling asleep for several hours.

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It wasn't until 6:30am the following morning, when they started bringing round breakfast, that the guards found Epstein unresponsive, according to court documents.

Prosecutors allege the two guards tried to cover up their failure by doctoring prison records.

Both have owned up to at least some of their failings, with Mr Thomas allegedly telling his supervisor: "We messed up … I messed up, she's not to blame, we didn't do any rounds."

First charges after Epstein's death

Epstein was arrested in July and charged with sex trafficking and sex trafficking conspiracy.

He could have faced up to 45 years in prison if found guilty.

He was accused of paying under-age girls to perform sex acts on him and his associates at his Manhattan and Florida mansions between 2002 and 2005.

The 66-year old was already a convicted sex offender, having been jailed in Florida in 2008 for procuring a minor for prostitution.

The Department of Justice reopened that case after an investigation by the Miami Herald exposed the lenient plea deal.

To date, 15 women have come forward to accuse Epstein of coercing them into illicit sex acts.

But his death has robbed them of their day in court, deeply embarrassed the US Bureau of Prisons and infuriated investigators who worked to bring the charges against him.

This is just the beginning of the investigation into his death

The FBI and the US inspector general are continuing to investigate the systemic failures that led to Epstein's death and have subpoenaed dozens more witnesses.

It's unclear how quickly that investigation will proceed. The Department of Justice did not return the ABC's request for comment.

Epstein's victims and US politicians are growing impatient.

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During a Senate hearing on Tuesday, Republican senator Lindsay Graham repeatedly asked the US Bureau of Prisons chief how Epstein managed to kill himself and whether there was any evidence to suggest it was not a suicide.

"With a case this high-profile, there's got to be either a major malfunction in the system or a criminal enterprise at foot to allow this to happen," he said.

He was perhaps referring to the whirl of conspiracy theories stipulating that Epstein was murdered.

Medical authorities say there is no doubt Epstein committed suicide, and surveillance footage shows no one accessed the area where his cell was located on the night he died.

What about the sex crimes investigation?

Epstein's death ended the case against him, which could have involved prominent figures including Prince Andrew, who has been accused of having sex with one of Epstein's victims, Virginia Giuffre, when she was 17.

In a BBC interview widely seen as a train wreck, Prince Andrew again denied any knowledge of the incident but that has not stopped calls for him to speak with US investigators about what he does know.

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Shortly after Epstein's death, US Attorney-General William Barr declared: "The victims deserve justice and they will get it".

"Let me assure you that this case will continue on against anyone who was complicit," he told a law enforcement conference in New Orleans."

It appears the FBI is still interviewing Epstein's victims as part of an ongoing investigation into possible accomplices.

While he denies any wrongdoing, legal experts say it is possible Prince Andrew could be subpoenaed.

Anna Rothwell, a lawyer at the British Law Firm Corker Binning, told the Times of London Prince Andrew is "not entitled to any form of immunity by virtue of his position as a member of the Royal family," and he would be "vulnerable to extradition".

In a fresh blow to the Duke of York, the Telegraph reports his name also appears in a cache of secret documents detailing new allegations against Epstein.

A judge in the US will reportedly decide before the end of the year whether to unseal the more than 3,000 pages of evidence which formed part of a defamation lawsuit in 2015.