Updated at 4 p.m. ET, April 28.

The parent company of Wikipedia is knowingly distributing child pornography, the co-founder of the online encyclopedia says, and he's imploring the FBI to investigate.

Larry Sanger, who left Wikipedia in 2002, said Wikimedia Commons (the parent company of Wiki products including Wikipedia, Wiktionary, Wikinews and Wikiquote) is rife with renderings of children performing sexual acts.

Sanger sent a letter to the FBI earlier this month outlining his concerns and identifying two specific Wikimedia Commons categories he believes violate federal obscenity law.

The first category, entitled “Pedophilia,” contains 25-30 explicit and detailed drawings of children performing sexual acts. The category was created three years ago.

The second, “Lolicon,” provides cartoons similar in detail and depiction. One of the more egregious cartoons shows a rendering of a young child about to perform oral sex on a much older man.

“I wasn’t shocked that it was online, but I was shocked that it was on a Wikimedia Foundation site that purports to be a reference site,” said Sanger, who is now involved in educational projects like Citizendium.org and WatchKnow.org, non-profit directories of videos for students grades pre-K to 12. (Wikimedia Commons is owned and hosted by the California-based Wikimedia Foundation.)

“I think a lot of teachers and education technologists responsible for the filters at public schools don’t realize how much and what level of pornography there is in the system. I’m quite sure that if they knew there were pages devoted to pedophilia, it might make them think twice about giving students unrestricted access in schools.”

Wikimedia’s general counsel did not respond to a request for comment. An e-mail sent to the foundation's press contact was not returned. Following publication of this article, both Moeller and Wikimedia posted responses online. See the update note at the end of this story.

After numerous phone calls and e-mails with an FBI spokeswoman over the span of three days —and despite multiple requests by the FBI for more time, including a weekend, to reply to a request for comment — the bureau on Monday refused to say whether it is investigating Wikimedia or following up on Sanger’s allegations.

Sanger says he began looking for explicit content after realizing during a mailing list discussion with other educators that most of them had no idea that Wikimedia had content that might be deemed inappropriate for students.

When Sanger’s research led him to graphic images of children, he looked up the law and realized that under the obscenity statute he’d homed in on, a person who sees obscene renderings of child abuse and does not report them to authorities is as culpable as the person who actually distributes the obscene content.

“I read, “You must report this to the FBI or else you are prosecutable under the same statute,” Sanger recalled. “And then I thought, 'Oh my.'”

That’s when he began composing his letter to the FBI.

He says burning bridges within the industry was not an easy thing to do, but he really didn't have a choice.

“I’m going to sound really old fashioned, but I felt that it was my duty. I really did,” he said.

“Wikimedia has quite a bit of pornography on it and they had no idea.”

But the threat is even greater than the images themselves, says James Marsh, an attorney who wrote about Sanger’s letter to the FBI on his Child Law Blog.

“Wikipedia’s continued interest in child sexual exploitation is troubling not only because the site hosts some questionable images, but because it can easily serve as a gateway to other sites containing child pornography," Marsh told FoxNews.com.

"One simple link buried in the text of an article on Japanese anime or child pornography could easily take an unsuspecting child or adult user to a place which is not only disturbing, but illegal.”

In addition to mentioning the two categories of possibly illegal content, Sanger also named the controversial high-level Wikipedia manager Erik Moeller, who Sanger said “is well known for his views in defense of pedophilia.”

“What is my position on pedophilia, then? It’s really simple. If the child doesn’t want it, is neutral or ambiguous, it’s inappropriate,” Moeller wrote in 2001 in a post on Kuro5hin.org that he titled, "Pleasure, Affection, Cause and Effect." These writings were drudged up by Valleywag in May 2008.

"The real issue for Wikipedia and sites like it is who is monitoring the content? Who is accountable? And who exactly is responsible? Anonymous editors and contributors and a complete lack of transparency presents a real risk of uncensored content being distributed worldwide. "

On his blog, he pointed out some of Moeller’s additions to Wikipedia articles:

To Wikipedia’s “Human Sexual Behavior” article, Moeller added:



"It is generally acknowledged that children are capable of feeling sexual pleasure, even if they are not yet able to engage in sexual intercourse with each other, and/or are not yet biologically able to reproduce."



To “Homosexuality and Morality,” he added:



“A small minority believes that children are capable of consenting to homosexual acts with older men, but all major pro-homosexual groups have rejected that view.”



Moeller, who did not reply to requests for comment, wrote into the “Pedophilia” entry:



"Again, someone who sexually abuses a minor is not necessarily a pedophile ('exclusively' 'attracted' to 'preadolescents' — emphasis on every word), but may simply be acting out of opportunity. The title 'pedophiles and pederasts' is redundant — pedophilia includes pederasty. This does not in any way mitigate the definitional problems of this article."

“I don’t think Wikimedia should be censored," Sanger said. "If they have decided to include pornography, then that ought to be their legal right. But I think the public ought to know that there’s a lot of that there.”

Sanger said he wants Wikimedia projects including Wikipedia to start using a consistent tagging system to mark all of its adult content and make it easy for filters to remove such content.

But Marsh thinks things are more serious than Sanger suggests.

“As Wikipedia becomes an authoritative source in law, politics and news, it makes a great target and medium for people with all kinds of questionable agendas,” he said.

“Wikipedia is like the Wizard of Oz. You never know exactly who is standing behind that green curtain. And that’s the real risk here.”

UPDATES:

-- Following publication of this article, Wikimedia Foundation posted an online response that reads in part:

“The Wikimedia Foundation obeys the law. In the weeks since Sanger’s published allegations, the Wikimedia Foundation has not been contacted by the FBI or any other law-enforcement agency with regard to allegedly illegal content on any Wikimedia projects. Our community of volunteer editors takes action to remove illegal material when such material is brought to its attention. The Wikimedia Foundation is proud of the Wikimedia editors who zealously work to keep the projects free of illegal material. If and when we are informed by law enforcement agencies of illegal content that has not already been removed through self-policing, we will take quick action to delete it.”

-- Erik Moeller also posted a response that reads in part:

“I want to say definitively: I do not defend nor support acts of sexual violence against children and have never defended pedophilia in any way.

“I have consistently defended the right of children of comparable age to engage in consensual, harmless sexual interactions with each other – what’s commonly called “playing doctor”, and also safe sex among teens. I have never defended the “right” of pedophiles to abuse children; child sexual abuse is a crime, and there is no such right. Children also don’t have the ability to consent to sexual activity with pedophiles, and such activities are sexual violence against children by definition.”

In response to the content mentioned in Larry Sanger’s letter to the FBI, Moeller wrote:

“It’s a false claim related largely to some historic early 20th century drawings, as described in the summary published by the Wikipedia Signpost. The Wikimedia Foundation’s General Counsel examined the drawings and concluded that they do not violate federal laws; we have not received any communication from the FBI to the contrary, and when and if we are asked by authorities to remove images that are illegal, we will do so.”

-- FoxNews.com has been informed that Sen. Sherrod Brown, D-Ohio, sent a copy of Sanger's letter to the FBI on April 21, and Rep. Steve Austria, R-Ohio, sent a copy of the same letter to the FBI on April 27.