British socialite Ghislaine Maxwell and others are under FBI investigation following the Jeffrey Epstein case, sources have told US and other media.
They face investigation over possible crimes linked to the sex trafficking charges laid against the US financier before he killed himself in August.
Ms Maxwell, a long-time Epstein friend, has not been accused by the authorities of wrongdoing.
Epstein had been charged with the sex trafficking of dozens of girls.
He was arrested earlier this year following allegations he was running a "vast network" of underage girls - some as young as 14 - for sex. He pleaded not guilty.
What details are there of the investigation?
The FBI investigation was initially reported by Reuters, quoting law enforcement sources. Neither Reuters nor other US news agencies who reached out to Ms Maxwell's lawyers received a response, and the FBI declined to comment.
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.
Reuters said there were no plans to interview Prince Andrew, as he did not fit into that category. Prince Andrew was also a friend of Epstein's. In November, the prince stepped away from Royal Family duties, saying the Epstein scandal had become a "major disruption" to the family.
The prince said he regretted his "ill-judged association with Jeffrey Epstein" but did not witness or suspect any suspicious behaviour during his visits to Epstein's homes.
Who is Ghislaine Maxwell?
Ms Maxwell is the daughter of late British media mogul Robert Maxwell and a former girlfriend of Epstein.
A well-connected socialite, she is said to have introduced Epstein to many of her wealthy and powerful friends, including Bill Clinton and the Duke of York.
She has mostly been out of public view since 2016 and her whereabouts are unknown.
An alleged Epstein victim, Virginia Giuffre, said in a civil lawsuit that Ms Maxwell had recruited her into the financier's circle, allegations Ms Maxwell denies.
Other women have also made allegations that Ms Maxwell was involved. One, Sarah Ransome, told the BBC's Panorama that Ms Maxwell "controlled the girls. She was like the Madam". Ms Maxwell has denied any involvement in, or knowledge of, Epstein's alleged abuses.
What happened to Epstein?
Allegations against Epstein had dated back years before the parents of a 14-year-old girl said he had molested her in 2005. Under a legal deal, he avoided federal charges and since 2008 was listed as level three on the New York sex offenders register.
But he was arrested again in New York on 6 July this year and accused of sex trafficking of underage girls. He was found unresponsive in his New York cell on 10 August and the death was later determined to be suicide.