Somaly Mam's story is incredible. Her autobiography, "The World of Lost Innocence," detailed how she was born in a village in the Cambodian rain forest and sold into sexual slavery as a child by her "grandfather." She was stuck in Southeast Asia's sex industry for 10 years until she finally escaped in her early 20s (her exact age isn't clear as she has no birth documents).

Mam began to settle into regular life, marrying a French man, moving to Europe and having children of her own. But her childhood experiences led her to save other girls who were suffering a similar fate. She returned to Cambodia and set up Acting for Women in Distressing Situations (known by its French acronym Afesip), a charity devoted to rescuing women and girls in Cambodia and neighboring Laos who are forced into prostitution.

Her efforts gained her international recognition – a 2009 appearance in the Time 100 was written by Angelina Jolie – and in turn raised millions for the protection of children and women from prostitution. But as incredible as that story is, its accuracy is now in serious doubt. On Wednesday, Gina Reiss-Wilchins, executive director of the Somaly Mam Foundation, a U.S.-based organization that acted as a fundraiser for Afesip, said that Mam had resigned from the foundation after being presented with the findings of an investigation by a California-based law firm, Goodwin Procter (Mam is not currently employed by Afesip).

While the exact details from Goodwin Procter have not been released, allegations of inconsistencies in Mam's past have been around for years. Doubts went back at least as far as 2012, when Mam gave a speech to the U.N. General Assembly that said that the Cambodian army had killed eight girls after a raid on her organization’s Phnom Penh center in 2004.

Following an investigation by Simon Marks in Cambodia Daily, Mam admitted that the claim was inaccurate. "I had in no way intended to allege that girls were murdered during the shelter raid,” Mam told Cambodia Daily in an e-mail, adding that her comments had been "ambiguous."

Later that year, Pierre Legros – Mam's French ex-husband – came forward to describe another incident that had not occurred as Mam had described it. In 2006, Mam told Mariane Pearl, wife of Daniel Pearl, in an article for Glamour Magazine that her teenage daughter had been abducted by human traffickers as revenge for her activism. Mam mentioned the incident again in her U.N. speech, which prompted Legros to respond. His daughter had in fact run away with a boyfriend, he said, claiming that he wanted to protect her privacy and stop her being used as “marketing” for the Somaly Mam Foundation.

The allegations about Mam's inaccuracies spread to other women linked with Afesip. Meas Ratha, who appeared with Mam on a prime-time French television show in 1998 and detailed a horrifying account of sexual slavery (an appearance that helped make AFESIP internationally famous), came out in 2013 to say that the story was fabricated and scripted by Mam. Long Pross, another woman associated with Mam, had told the New York Times' Nicholas Kristoff that she had her eye stabbed out when she refused to have sex with a customer while being forced to be a prostitute. In a 2012 article, Cambodia Daily interviewed two people who said they were the parents of Long Pross and that their daughter was never the victim of sex trafficking and that her eye had been removed due to a non-malignant tumor.

It wasn't until this year that the Somaly Mam Foundation began investigating its founder, after a Newsweek reporter began making multiple requests for an interview with Mam. In May, Newsweek published a long article detailing the above allegations, and going even further on new ones. The author of that article was Simon Marks, who broke many of the above stories for Cambodia Daily. Marks never got to speak to Mam, but he spoke to people who claimed to know Mam as a child who said she had lived a relatively normal life with her parents. His article cast doubt on her more recent behavior, too, speaking to one former volunteer with Afesip who described Mam as "tyrannical," "moody," "erratic" and "entitled" when other people are not around.

If such allegations are really true, Mam would hardly be the first activist accused of fabricating her background. Rigoberta Menchú, a Guatemalan woman and Nobel Prize-winning activist who shone a light on the treatment of indigenous peoples, was attacked for alleged fabrications in her own biography in the late 1990s (and those allegations were in turn criticized some years later).

Some argue that the practice of exaggerating stories is widespread among activists. “[I] find it unfair to point solely at Afesip for fabricating stories about its typical beneficiaries. This has been and still is the approach that all major international NGOs use, in Cambodia and elsewhere,” Pierre Fallavier, a former adviser for Afesip, told Cambodia Daily last year. “They take bits and parts of the life stories of different beneficiaries and make up a ‘typical’ sob story that they use to raise funds with.”

Right now, however, it's unclear whether any of the above allegations led directly to Mam's resignation: Reiss-Wilchins's statement contains little specifics, and a spokesperson for the foundation declined to comment further. However, the statement does go some way to show that, even if some of it was fabricated, Mam's story created some good.

"We have touched the lives of over 100,000 women and girls," the statement reads. "We have treated nearly 6,000 individuals at a free medical clinic in Phnom Penh’s red light district and engaged nearly 6,400 students in anti-trafficking activism [...] Our work changes lives and we remain dedicated to it."

A 2012 report from the foundation says it raised more than $2.8 million that year.

Update: I'd like to point readers to two convincing articles about the potential costs and risks created by Mam's alleged fabrications. "The Price of a Sex-Slave Rescue Fantasy" by Melissa Gira Grant at the New York Times, and "Here’s why it matters when a human rights crusader builds her advocacy on lies" by Anne Elizabeth Moore at Salon.

Correction: This post originally said that the Somaly Mam Foundation began it's investigation after Newsweek's article was published. The investigation in fact began after Newsweek's reporter Simon Marks made multiple requests for an interview with Mam. The post has been updated to correct this.