Federal prosecutors on Monday announced sex trafficking and conspiracy charges against the 66-year-old Epstein, who was arrested Saturday related to alleged incidents in Florida and New York City.
Court documents unsealed Monday show Epstein is charged with creating and maintaining a network that allowed him to sexually exploit and abuse dozens of underage girls, with alleged victims as young as 14 at the time.
Prosecutors said the evidence included a "vast trove" of hundreds or even thousands of lewd photographs of young women or girls, discovered in a search of his New York mansion after his arrest.
That mansion is still set up the way victims described it 15 years ago, prosecutors said, with a private "massage room" containing a massage table and sex toys.
"The government's evidence is strong," Assistant US Attorney Alex Rossmiller said, adding that victims provided "detailed, credible and corroborated " information. He said several additional victims have come forward since Epstein's arrest.
Authorities say he paid underage girls for massages and then molested them at his homes in both states in the early 2000s. He "intentionally sought out minors and knew that many of his victims were in fact under the age of 18," prosecutors said.
He also paid some of his victims to "recruit additional girls to be similarly abused by Epstein," the indictment says. "In this way, Epstein created a vast network of underage victims for him to sexually exploit in locations including New York and Palm Beach."
Epstein appeared in Manhattan federal court later Monday in a blue jail uniform, his hair disheveled, and pleaded not guilty. He was ordered jailed at least until a bail hearing Thursday, when prosecutors planned to argue that the world traveler might flee - or try to intimidate witnesses - if released on bail.
"He is extraordinarily wealthy," Rossmiller said, detailing six residences and two private jets. "He has every motivation in the world to flee, and he has the means to do it."
WATCH: US Attorney news conference announcing sex charges against Epstein
Epstein's arrest was first reported by The Daily Beast, and sources tell ABC News that Epstein was picked up at New Jersey's Teterboro Airport on Saturday after returning to the United States from France.
The arrest was the result of a joint investigation by the FBI and the NYPD and comes amid renewed scrutiny of a once-secret plea deal that ended a federal investigation against him.
That deal, which is being challenged in Florida federal court, allowed Epstein, who is now 66, to plead guilty to lesser state charges of soliciting and procuring a person under age 18 for prostitution.
Averting a possible life sentence, Epstein was instead sentenced to 13 months in jail. The deal also required he reach financial settlements with dozens of his once-teenage victims and register as a sex offender.
U.S. Attorney Geoffrey Berman of New York said that the non-prosecution agreement that spared Epstein from a heavy prison sentence on similar allegations a decade ago is binding only on federal prosecutors in Florida, where the deal was made, not on authorities in New York.
"While the charged conduct is from a number of years ago, it is still profoundly important to the many alleged victims - now young women," Berman said. "They deserve their day in court. We are proud to be standing up for them by bringing this indictment."
Epstein is a wealthy hedge fund manager who once counted as friends former President Bill Clinton, Great Britain's Prince Andrew, and President Donald Trump.
In his most extensive known public comments about Epstein, Trump told New York magazine in 2002 that he'd known the financier for 15 years and praised him as a "terrific guy."
"He's a lot of fun to be with," Trump was quoted as saying. "It is even said that he likes beautiful women as much as I do, and many of them are on the younger side. No doubt about it - Jeffrey enjoys his social life."
Trump Organization attorney Alan Garten has since distanced Trump from Epstein, telling Politico in 2017 that Trump "had no relationship with Mr. Epstein and had no knowledge whatsoever of his conduct."
Former federal prosecutor David Weinstein said there's almost no chance Epstein will be allowed to go home after the hearing. Under federal court rules, prosecutors can keep a defendant locked up for three extra days while preparing for a bail hearing without needing a reason. If that happens in Epstein's case, it would mean a bail hearing on Thursday.
"The government is clearly seeking to have him detained," Weinstein said. "The guy is a millionaire or a billionaire. He has unrestrained assets. If they let him out on a bond, he may take off, go to a jurisdiction where they don't have extradition and they may never get him back."
Under the deal, overseen by former Miami U.S. Attorney and current Trump labor secretary Alexander Acosta, Epstein avoided a possible life sentence and served 13 months in jail after pleading guilty to Florida charges of soliciting and procuring a person under age 18 for prostitution.
Acosta has defended the plea deal as appropriate under the circumstances, though the White House said in February that it was "looking into" his handling of the deal.
U.S. District Judge Kenneth Marra of Florida ruled earlier this year that Epstein's victims should have been consulted under federal law about the deal, and he is now weighing whether to invalidate the deal.
Federal prosecutors recently filed court papers in the Florida case contending Epstein's deal, known as an NPA, must stand.
"The past cannot be undone; the government committed itself to the NPA, and the parties have not disputed that Epstein complied with its provisions," prosecutors wrote in the filing.
They acknowledged, however, that the failure to consult victims "fell short of the government's dedication to serve victims to the best of its ability" and that prosecutors "should have communicated with the victims in a straightforward and transparent way."
(The Associated Press contributed to this report.)