The sources familiar with the investigation said the principal focus is Maxwell and other “people who facilitated” allegedly illegal behaviour.
Maxwell, along with others, faces investigation over possible crimes which they may have facilitated linked to sex trafficking charges which were laid against the US billionaire financier before he killed himself in his prison in New York in August.
However, whilst Maxwell is the main focus of the FBI investigation she has not been accused of committing a crime.
The inquiry is believed to be in the early stages and no new charges are pending.
The sources have not revealed any other names of those being investigated or more details of any possible crimes, beyond saying it concerned people who may have facilitated Epstein’s alleged actions.
Epstein was arrested in July charged with trafficking dozens of underage girls as young as 14 from at least 2002 to 2005.
Women who came forward to make allegations against Epstein claim Maxwell recruited them as young, vulnerable teenagers to perform massages on Epstein, which then became sexual encounters.
Some victims have accused Maxwell of also taking part in the sexual abuse.
Maxwell is keeping a low profile and is now believed to be living in a friend’s seafront mansion in Massachusetts.
The FBI is understood to be examining potential leads from a hotline for Epstein’s accusers set up following his arrest in July and its investigation remains in its early stages, according to the source which cited multiple law enforcement sources.
Lawyers for Maxwell have not responded to requests for a comment.
Virginia Giuffre, one of Epstein’s alleged victims, has said in a civil lawsuit that Maxwell recruited her into Epstein’s circle, where she claims Epstein forced her to have sex with him and friends including the Duke of York.
Maxwell called Giuffre’s allegations lies. Giuffre then filed a defamation suit against Maxwell in 2015.
The source said there were no current plans to interview the duke, a close friend of both Epstein and Maxwell.
The duke, who visited Epstein at his home in New York and stayed on his private island, retired from public life last month after a disastrous television interview where he failed to acknowledge the suffering caused to Epstein’s alleged victims.
Gloria Allred, the lawyer for five of Epstein’s alleged victims, all of whom have spoken to law enforcement, said that reports the FBI is investigating Maxwell “are not surprising” because “Ms Maxwell was part of Jeffrey Epstein’s inner circle for many years.”
“Since the US justice department has stated that it would continue their investigation into anyone who may have knowingly conspired with Epstein to sex traffic underage girls, it would be logical that the FBI would want to interview anyone in Epstein’s inner circle, including Ms Maxwell, to determine who may or may not have assisted Epstein in committing his crimes against children.”
Allred added: “Jeffrey Epstein could not have committed his crimes without the assistance of others. If there is sufficient evidence to prove that others may have criminal culpability, then they should be charged and be accountable in a court of law.”