Such injuries can occur to people who hang themselves or who are strangled.

Epstein was found dead in an apparent suicide in his jail cell in New York City on Saturday.

He had been awaiting trial on sex trafficking charges.

The circumstances of the multi-millionaire's death are under investigation, and it was unclear when a report of the autopsy will be made public.

A representative of the New York Medical Examiner's office did not immediately respond to requests for comment.

One of the two law enforcement sources familiar with the Epstein case said there was no evidence or suggestion of foul play, but cautioned the investigation was still at an early stage.

Bergen County medical examiner in New Jersey Dr Zhongxue Hua said a neck fracture was atypical in a suicide, but warned not to jump to conclusions.

"It's unusual to have a neck fracture," Hua said. "But the first question to address is when did it occur."

If Epstein's neck fracture was fresh, Hua said, then "at a minimum, it's a very unusual suicide".

Epstein, 66, who once counted US President Donald Trump and former president Bill Clinton as friends, was found unresponsive in his cell on Saturday morning, according to the Federal Bureau of Prisons.

Epstein had pleaded not guilty in July to charges of sex trafficking involving dozens of underage girls between 2002 and 2005.

Prosecutors said he recruited and paid girls to give him massages, which became sexual in nature.

Attorney General William Barr has said the criminal investigation into any possible co-conspirators would continue.

Barr, whose agency oversees the Bureau of Prisons, has also demanded an investigation into Epstein's death and ordered the removal of the prison's warden.

The disgraced financier had been on suicide watch at the Metropolitan Correctional Center in lower Manhattan but was taken off prior to his death, according to a source.

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