Disgraced US financier Jeffrey Epstein has been found dead in a US prison.

Officials and US news media reported that he died by suicide while awaiting trial on charges that he trafficked underage girls for sex.

Epstein, a convicted pedophile who befriended numerous politicians and celebrities over the years, was found unresponsive in his cell at the Metropolitan Correctional Centre from "an apparent suicide", the US Department of Justice said.

He was discovered around 6.30am local time (12.30pm Irish time) and rushed to hospital in New York where he was pronounced dead, it added in a statement.

"The FBI is investigating the incident," the department said.

The city medical examiner's office confirmed Epstein's death but said nothing about what caused it. It said a medical investigation has been opened.

Epstein's death comes a day after a tranche of sealed legal documents were released for the first time providing new details about what prosecutors allege was Epstein's sex-trafficking operation.

It also comes just over two weeks after the 66-year-old was found unconscious in his cell after an apparent suicide attempt.

Epstein did not appear to be showing any visible signs of injuries when he appeared in court on 31 July following that incident, to be told that his trial would not begin before June next year.

The hedge fund manager had been charged with one count of sex trafficking of minors and one count of conspiracy to commit sex trafficking of minors.

He was denied bail last month in a New York court because he was deemed a flight risk.

Epstein denied the charges and had faced up to 45 years in prison - effectively the rest of his life - if convicted.

The Metropolitan Correction Centre, a federal facility in Manhattan that is often used to house suspects awaiting or during trial, is considered one of the most secure penal establishments in the US.

Epstein's death quickly raised questions about how he could take his own life despite reportedly being put on suicide watch after his first failed attempt.

"We need answers. Lots of them," tweeted New York Congresswoman Alexandria Ocasio-Cortez.

Yesterday, 2,000 pages of documents focusing on testimony by a victim who claimed she was a "sex slave" of Epstein were released by a New York court.

Prosecutors said Epstein sexually exploited dozens of underage teenagers, some as young as 14, at his homes in Manhattan and Palm Beach, Florida, between 2002 and 2005.

They claim that Epstein was "well aware that many of the victims were minors".

The girls were paid hundreds of dollars in cash to massage him, perform sexual acts and to recruit other girls, prosecutors allege.

They say Epstein had an army of recruiters, often not much older than their targets, who would approach vulnerable teens.

Epstein is also accused of paying off possible co-conspirators to "influence" them, US media have reported.

Epstein was convicted previously of paying young girls for sexual massages at his Palm Beach mansion.

He avoided federal prosecution under a plea deal that required him to admit to a single Florida state charge of soliciting prostitution from a minor and register as a sex offender.

He served 13 months in a county jail before being released in 2009.

Last month, Alex Acosta resigned as US labour secretary amid a backlash over the deal that he negotiated with Epstein in that case while he was a federal prosecutor in Florida.