His body was discovered at 7.30 a.m.
He was arrested on July 6, and pleaded not guilty to charges of sex trafficking.
However, in a court filing last month, the government said it was pursuing an "ongoing investigation of uncharged individuals" connected to Epstein, and US Attorney Geoffrey Berman confirmed on Saturday that the investigation will continue despite Epstein's death.
Epstein hanged himself and his body was found at about 7:30 a.m. on August 10 at Metropolitan Correctional Center in Manhattan.
In 2015, Ms Maxwell was sued for defamation by Virginia Roberts Giuffre, an alleged victim of Epstein who claimed she had been recruited as a "sex slave" by Epstein and groomed from the age of 15.
Then, in a much-quoted 2002 New York Magazine interview, Mr Trump described Epstein as a "terrific guy" and even acknowledged that he liked women "on the younger side".
The billionaire had numerous powerful and influential friends - including Bill Clinton and US President Donald Trump.
He avoided similar charges in a controversial secret plea deal in 2008, and instead pleaded guilty to a lesser charge.
Epstein and Mitchell did know each other, but there was never any hint that Mitchell was in any way involved in Epstein's sex ring.
Epstein's lawyers say the federal charges that accuse Epstein of recruiting and abusing dozens of underage girls in NY and Florida in the early 2000s should never have been brought.
"Jeffrey Epstein's victims have once again been cheated out of an opportunity for justice", said Jack Scarola, a Florida attorney who represented five women and litigated with him for 12 years.
The FBI said it was probing the death of alleged billionaire sex trafficker Jeffrey Epstein while in custody early Saturday.
Epstein had denied the current charges against him.
Epstein was asked in the videotaped deposition whether it was standard operating procedure for his former girlfriend, Ghislaine Maxwell, to bring underage girls to him to sexually abuse.
After Epstein's arrest, prosecutors said a search of his townhouse, conducted under a warrant, uncovered evidence of hundreds, and perhaps thousands, of nude photographs of "what appeared to be underage girls", including some photos catalogued on compact discs and kept in a locked safe.
"At the end of the day, based on the evidence, professionals within a prosecutor's office decided that a plea that guarantees someone goes to jail, that guarantees he register [as a sex offender] generally and guarantees other outcomes is a good thing, '" Acosta said in March 2017. However, if you or someone else is in danger or endangering others, call police immediately on 111.