A liquor heiress is facing charges of funding a suspected US sex cult whose recruits were allegedly branded with the initials of its founder.
Seagram scion Clare Bronfman, 39, is accused of using her fortune to help finance Nxivm's operations.
Investigators say the organisation is a sex-trafficking operation disguised as a mentoring group.
Six people have now been charged as part of the inquiry, including 35-year-old Smallville actress Allison Mack.
Ms Bronfman's lawyer said her client "did nothing wrong".
She was formally charged on Tuesday before being released on a $100m (£75m) bail bond.
What is Nxivm?
On its website Nxivm (pronounced nexium) describes itself as a "community guided by humanitarian principles that seek to empower people and answer important questions about what it means to be human".
Based in Albany in upstate New York, the group was founded as Executive Success Programs in 1998 and says it has worked with more than 16,000 people.
Members of the group are reported to include the son of a former Mexican president and Hollywood actresses.
Federal prosecutors allege Nxivm's leader Keith Raniere, 57, oversaw a "slave and master" system within the group. Female members were expected to have sex with him and were branded with his initials, say former members.
According to the group's website, it has suspended enrolment and events because of the "extraordinary circumstances facing the company at this time".
What is Clare Bronfman accused of?
Ms Bronfman, the daughter of late billionaire philanthropist and Seagram head Edgar Bronfman, was arrested on Tuesday along with three others on charges of racketeering conspiracy, US prosecutors say.
Court documents allege Ms Bronfman, a member of Nxivm's executive board, was involved in the identity theft of at least two women - including a deceased sexual partner of Mr Raniere.
She is also accused of encouraging and assisting in an alleged Nxivm victim's illegal entry into the US.
In a note published on her website last December, Ms Bronfman said she still supported Nxivm after seeing "so much good come from both our programmes and from Keith himself".
Her lawyer Susan Necheles said in a statement that Nxivm was "not a criminal enterprise" but "an organisation that helped thousands of people," according to US media.
"The charges against Clare are the result of government overreaching and charging an individual with crimes just because the government disagrees with some beliefs taught by Nxivm and held by Clare," Ms Necheles said.
Who else has been charged?
Keith Raniere himself was arrested by the FBI in Mexico in March.
He and actress Allison Mack were charged with sex trafficking and forced labour conspiracy the following month.
Both face mandatory minimum sentences of 15 years and a maximum of life imprisonment for the sex-trafficking charges.
Mr Raniere, whose trial is scheduled for 1 October, has been denied bail because of fears that Ms Bronfman might use her financial clout to help him escape.
Nxivm co-founder Nancy Salzman, 64, her daughter, Lauren Salzman, 42, and the group's 60-year-old bookkeeper, Kathy Russell, were all arrested alongside Ms Brofman on Tuesday.
All six are accused of racketeering conspiracy, or attempting to illegally obtain or extort money, and could face up to 20 years in jail, plus an additional maximum 15 years for identity theft conspiracy.
The US Department of Justice says the group committed "an array of crimes, including identity theft, extortion, forced labour, sex trafficking, money laundering, wire fraud and obstruction of justice".
FBI Assistant Director-in-Charge William Sweeney said on Tuesday that "the details of these alleged crimes become more and more grim as we continue to dig deeper into the conduct of this organisation and its intended mission".