Now, Fox News has exclusively learned that residents still living in the neighborhood where the alleged activity occurred are "terrified."
Investigation Discovery (ID) aired "The Lost Women of NXIVM" documentary on Sunday, in which investigator Frank Parlato explored whether or not Raniere, 59, played a role in four of his ex female roommates contracting various forms of cancer.
One female, who survived bladder cancer after living with Raniere for years in his Halfmoon, N.Y. condo, submitted a hair sample to forensic expert Jason Kolowski in the film. The results showed the woman, who wished to remain anonymous, had "significantly higher" traces of "heavy metals" known as barium and bismuth than what's considered normal.
The metals are found in "gun powder, explosives, electronic devices" in addition to "rat poison," Kolowski claimed.
Raniere's rumored live-in girlfriends, Barbara Jeske and Pam Cafritz, died of brain and kidney cancer, respectively. Former NXIVM member Kristin Keeffe survived cervical cancer after having a relationship with Raniere.
The Halfmoon neighbor told Fox News that several citizens in the Knoxwood condominium complex where Raniere lived now believe he poisoned these women in an effort to weaken their immune systems.
"I don't think it's a coincidence anymore," the resident said. "It's kind of weird that these women all got sick in the same house."
The neighbor, who recalled witnessing Raniere walk around the neighborhood late at night with "younger" women before his March 2018 arrest, called him "beyond evil."
"This documentary has made the neighbors very nervous again," the resident continued.
"Even though he's locked up in prison, I want to get a home alarm system. All this crap was going on right under my nose. We shouldn't have to feel insecure anymore."
The enraged resident added: "In my opinion, NXIVM is not dead."
The documentary also investigated the presumed death of former NXIVM member Kristin Snyder. Snyder disappeared in Alaska in 2003 after leaving behind an alleged suicide note.
Snyder's body has never been found. The missing woman informed NXIVM members she was pregnant with Raniere's child before allegedly drowning in a kayak in Resurrection Bay, the documentary reveals. Her pal Susan Dones told Fox News she believes the suicide tale is "fishy."
"The more I asked questions, the more I received angry responses from leadership of NXIVM," Dones said. "This was supposed to be an organization of compassion and humanity. Why are you angry at me for asking questions?"
Raniere was found guilty of seven felonies, including racketeering and sex trafficking, in June. Prosecutors say Raniere was a con man who peddled expensive self-fulfillment courses for the purported self-help group as a cover for mentally and sexually abusing female followers.
"Smallville" actress Allison Mack was also a high-profile member of the cult and labeled by prosecutors as a "slave master" of the corrupt organization's inner sex ring, known as "DOS." She pleaded guilty to racketeering charges earlier this year and is awaiting a sentencing date.
Raniere is currently housed in the Metropolitan Detention Center in Brooklyn and is expected to be sentenced in January.
Fox News' Stephanie Nolasco contributed to this report.