Keith Raniere, the co-founder and leader of NXIVM, will remain in federal custody and be returned to New York later this week to face federal charges of sex trafficking and conspiracy to commit forced labor.

Raniere was shackled and dressed in a T-shirt, athletic shorts and sneakers — similar to the clothes he was wearing as he was arrested Sunday near Puerto Vallarta, Mexico — when he was brought before a U.S. magistrate on Tuesday afternoon in Fort Worth, Texas. Raniere declined to speak with reporters and said only, "Yes, Your Honor," when he was asked by the judge if he understood his rights.

Assistant U.S. Attorney Moira Penza, who is leading the investigation for the U.S. attorney's office in Brooklyn, attended the brief proceeding but did not speak. Raniere was represented by a criminal defense attorney from Fort Worth, who told the judge that Raniere would waive his right to challenge his extradition from the Eastern District of New York.

Three people who appeared to be supporters of Raniere's attended the brief proceeding but declined to speak to reporters. Another man, who said he is from Mexico and had driven to Texas to attend the proceeding, said he was "concerned but not worried" about Raniere's arrest. He declined to give his name.

Raniere will remain in the custody of U.S. marshals without bond pending his return to New York. A warrant for his arrest was issued Feb. 14, after federal prosecutors filed a sealed complaint in Brooklyn charging Raniere with several felony counts.

The extraordinary arrest of Raniere marks the downfall of the leader of an international "self-help" organization that has been headquartered in the Capital Region for roughly two decades. Some experts have described NXIVM as a cult, and the criminal prosecution of Raniere has forced the secretive man who calls himself "Vanguard" out of the shadows and under the spotlight of an ongoing federal criminal investigation.

The federal criminal complaint accuses Raniere of forming a group within NXIVM in which women said they were coerced into joining a slave-master club. The women, some of whom said they were pressured to have sex with Raniere, told federal authorities that a female doctor associated with NXIVM used a cauterizing iron to brand them with a design on their lower abdomen that contained the initials of Raniere and Allison Mack, an actress and NXIVM associate who is listed in the complaint as an unnamed co-conspirator.

Raniere was taken into custody by Mexican federal police who tracked him to a $10,000-a-week villa near Puerto Vallarta, where he was staying with several women, federal officials said.

In court filings, U.S. Justice Department officials said that Raniere fled to Mexico last November when the federal investigation began. They have asked for him to be detained without bond while the case is pending, describing him as a flight risk and danger to the community.

Federal authorities said Raniere has access to millions of dollars and private jets, and that he stopped using his mobile phone and began using encrypted email after he arrived in Mexico, which made him difficult to locate.

Warning: The document below contains graphic depictions of alleged sexual activity.

In the hours preceding Raniere's court appearance in Texas, FBI agents spent several hours combing through the Saratoga County residence of NXIVM's co-founder and president, Nancy Salzman.

The FBI's raid of Salzman's residence signaled a wider criminal investigation of the secretive organization than just the sex-trafficking allegations that led to the arrest this week of its longtime leader.

A former NXIVM associate, Kristen M. Keeffe, who defected from the organization several years ago, alleged in 2015 that large amounts of cash used to be stored in a safe at Salzman's residence.

The allegations made by Keeffe were contained in a transcript of a telephone conversation that took place in March 2015 between Keeffe and Barbara J. Bouchey, a former NXIVM executive board member who was facing computer trespassing charges at the time. Bouchey and three others were accused by NXIVM of of improperly accessing the corporation's website, but the charges against Bouchey and two others were dismissed.

While Bouchey's case was pending, her attorneys filed a copy of the transcript to buttress their argument that top NXIVM officials have used litigation, as well as the criminal case, to attack her and other perceived adversaries. Keeffe described many of those tactics during the lengthy conversation, and also provided allegations about Salzman.

Keeffe, who was part of Raniere's inner circle for many years, told Bouchey that money collected from people who took NXIVM training sessions in Mexico was funneled across the border into the United States. She claimed that Salzman, among others, would allegedly "bring the cash over the border."

The money, which was allegedly funneled through the bank account of a Mexican associate, was "logged on the system as a scholarship and cash was kept in Nancy's house," Keeffe said.

"And the cash for a certain time period, I doubt it's still there, was kept in a safe in Nancy's house," Keeffe added during the recorded conversation. "If Keith ever had to go into hiding it was Keith's off-the-grid fund. And the last time I heard about it, there was two and a half million dollars in it."

In a federal court filing this week, the Justice Department said that for the past 18 months Raniere had been using a credit card and bank account in the name of a former NXIVM associate and girlfriend, Pamela Cafritz, who died in November 2016. Federal prosecutors said the bank account holds about $8 million.

Salzman has been an influential figure in the organization since it was set up more than two decades ago. She also was involved in some of the medical research studies that were performed by a doctor associated with NXIVM, Brandon B. Porter.

On Sunday, the Times Union reported that New York Attorney General Eric Schneiderman's office is conducting a separate investigation of a nonprofit foundation associated with NXIVM that allegedly sponsored brain-activity and other human behavioral studies without any apparent oversight, according to court records.

The nonprofit Ethical Science Foundation was formed in 2007 by Clare E. Bronfman, who owns a horse farm in Delanson and is listed in public records as the trustee and donor of the foundation.

At the request of the attorney general's office, a state Supreme Court justice recently signed an order directing Bronfman and Porter, who is involved with NXIVM and conducted the human studies, to turn over all documentation associated with the research, including any written communications, videos, conclusions, consent forms and the names and addresses of "individuals associated with Ethical Science Foundation who participated in any manner with the studies."

A Vancouver woman, Jennifer Kobelt, said in a complaint filed with the state Health Department last year that a bizarre experiment she was subjected to by Porter took place in a small commercial building in Halfmoon that has been used for years by NXIVM for training and seminars.

Kobelt said she was recruited for the study by an assistant of Salzman and that she knew of at least four other women who took part.

Barry Shlachter contributed reporting from Fort Worth, Texas.