New York City's chief medical examiner says an autopsy has been performed on Jeffrey Epstein but that more information is needed before a cause of death determination is made.

Dr. Barbara Sampson said in a statement that a city medical examiner performed the autopsy Sunday while a private pathologist observed the examination at the request of Epstein's representatives.

The private pathologist, Dr. Michael Baden, was the city's chief medical examiner in the late 1970s and has been called as an expert witness in high-profile cases including by the defence at O.J. Simpson's 1994 murder trial.

Sampson says having a private pathologist observe an autopsy is a routine practice.

The U.S. Federal Bureau of Prisons has said Epstein was found unresponsive in his cell at a Manhattan jail early Saturday. The agency called his death an apparent suicide.

Jail may have been understaffed

Guards on Epstein's unit were working extreme overtime shifts to make up for staffing shortages when he died, a person familiar with the jail's operations tells The Associated Press.

The person familiar with the Metropolitan Correctional Center's operations told The Associated Press on Sunday that one guard in Epstein's unit was working a fifth straight day of overtime and another guard was working mandatory overtime. The person spoke on condition of anonymity because he lacked authorization to discuss jail operations publicly.

The jail staff failed to follow protocols leading up to Epstein's death, according to a report from the New York Times, deepening the need for a probe into what led to the highly connected financier's apparent suicide.

Epstein should have been checked on by guards in his cell every 30 minutes, but that didn't happen the night before his apparent suicide, a law enforcement official told the Times.

A law enforcement source also said he was alone in his cell Friday night after his cellmate was transferred. An official with knowledge of the investigation told the Times that the Justice Department was told Epstein would have a cellmate and be monitored by a guard every 30 minutes.

He was found unresponsive in his jail cell Saturday, and the Bureau of Prisons says he was later pronounced dead of an apparent suicide.

Epstein's death weeks after he was indicted on sex-trafficking charges has raised a range of questions about how such a high-profile detainee could die in custody.

The city's former mayor, Rudy Giuliani, now a lawyer for U.S. President Donald Trump, tweeted out several questions about Epstein's death.

What does the word watch mean in the phrase suicide<br>Watch? Who was watching? What does camera show? It is inconceivable Epstein could have hung himself if there was a suicide Watch? Follow the motives. —@RudyGiuliani

"Who was watching? What does camera show? ... Follow the motives," Giuliani tweeted Saturday afternoon after news broke that the multimillionaire businessman's body had been found in his jail cell in the morning.

Epstein, 66, had been taken off suicide watch at the end of July, sources told U.S. media outlets. He was reportedly placed temporarily on a suicide watch after he was found July 23 in his cell with marks on his neck.

Hours after the Federal Bureau of Prisons announced that Epstein was found unresponsive in his cell at the Metropolitan Correctional Center (MCC) and then pronounced dead in hospital, #EpsteinMurder was trending worldwide on Twitter, and the U.S. president joined Twitter speculation around Epstein's death while under the federal government's watch.

Trump, who rose to conservative prominence by falsely claiming Obama wasn't born in the U.S., retweeted unsubstantiated claims about Epstein's death.

Other politicians also took to social media to question the circumstances.

Republican Sen. Rick Scott of Florida, the state where some of Epstein's alleged sexual abuse crimes took place, suggested the possibility that others might have been involved in Epstein's death when he called on corrections officials to explain what happened.

"The Federal Bureau of Prisons must provide answers on what systemic failures of the MCC Manhattan or criminal acts allowed this coward to deny justice to his victims," he tweeted.

Jeffrey Epstein died by apparent suicide Saturday at the Metropolitan Correctional Center in Manhattan. This July 30, 2008, file photo shows Epstein in custody in West Palm Beach, Fla. He was arrested July 6 of this year on federal sex-trafficking charges. (Uma Sanghvi/Palm Beach Post/The Associated Press)

The FBI and the U.S. Department of Justice's Office of the Inspector General will investigate the circumstances surrounding Epstein's death, Attorney General William Barr said.

"Mr. Epstein's death raises serious questions that must be answered," Barr said in a news release in which he said he was "appalled" to learn of the apparent suicide.

'Every single person' knew about suicide risk

Joining those demanding accountability is Sen. Ben Sasse, a Republican from Nebraska and chair of the Senate judiciary oversight committee who had asked the U.S. Justice Department to investigate the handling of the Epstein case.

"Every single person in the Justice Department — from your Main Justice headquarters staff all the way to the night-shift jailer — knew that this man was a suicide risk, and that his dark secrets couldn't be allowed to die with him," Sasse wrote Saturday in a letter addressed to Barr.

Given Epstein's previous attempted suicide, he should have been locked in a padded room under unbroken, 24/7, constant surveillance," Sasse wrote.

"Obviously, heads must roll," he added.

Epstein's suicide was likely recorded by jail cameras, according to Preet Bharara, the former federal prosecutor in Manhattan.

"One hopes it is complete, conclusive, and secured," he tweeted, referencing video he said should exist.

There should be — and almost certainly is — video of Epstein’s suicide at MCC. One hopes it is complete, conclusive, and secured. —@PreetBharara I’m dumbfounded also, <a href="https://twitter.com/JamesAGagliano?ref_src=twsrc%5Etfw">@JamesAGagliano</a>. It’s possible Epstein was placed on suicide watch for some time and then returned to the SHU, prematurely. DOJ says FBI is investigating. Public deserves answers. <a href="https://t.co/sGXXjNbUTk">https://t.co/sGXXjNbUTk</a> —@PreetBharara

Epstein's arrest on July 6 launched separate investigations into how authorities handled his case initially when similar charges were first brought against him in Florida more than a decade ago. U.S. Labour Secretary Alexander Acosta resigned last month after coming under fire for overseeing that deal when he was U.S. attorney in Miami.

The New York City medical examiner's office, the FBI and the inspector general's office of the U.S. Justice Department have all launched investigations into why Epstein had not remained under special monitoring.

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.

Epstein's abrupt death cuts short a criminal prosecution that could have pulled back the curtain on the inner workings of the high-flying financier with connections to celebrities and presidents, though prosecutors have vowed to continue investigating.

Epstein had been denied bail and faced up to 45 years behind bars on federal sex-trafficking and conspiracy charges unsealed last month. He had pleaded not guilty and was awaiting trial.

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

What happens next for Epstein's accusers

Several of Epstein's accusers said Saturday that they're disappointed that the financier won't have to face them in court or serve a long prison sentence if convicted. They called on federal authorities to investigate associates of Epstein for any role in his activities.

Annie Farmer, left, and Courtney Wild, right, two of Jeffrey Epstein's accusers, stand outside the courthouse in New York in July. (Seth Wenig/Associated Press)

Sigrid McCawley, an attorney representing one accuser, said in a statement that "the reckoning of accountability begun by the voices of brave and truthful victims should not end" with Epstein's death.

Another accuser, Jennifer Araoz, who came forward after the new charges were filed, said she was angered by Epstein's suicide. Araoz alleged that Epstein raped her in his New York mansion in the early 2000s when she was 15.

"We have to live with the scars of his actions for the rest of our lives, while he will never face the consequences of the crimes he committed, the pain and trauma he caused so many people," she said.

Brad Edwards, a Florida lawyer for nearly two dozen other accusers, said that "this is not the ending anyone was looking for."

"The victims deserved to see Epstein held accountable, and he owed it to everyone he hurt to accept responsibility for all of the pain he caused," Edwards said in a statement.

Lisa Bloom, a lawyer representing some of Epstein's alleged victims, tweeted after his death that civil cases will proceed against his estate. She added that her clients would have liked him to live to "face justice."

She later added a statement from an alleged victim who says, "I will never have a sense of closure now."