In what may be an orchestrated hoax targeting Planned Parenthood, at least 11 of the abortion provider's health centers were, in a one-week span, visited by men who implied they ran interstate sex trafficking rings involving teenagers and undocumented immigrants.

Planned Parenthood reported the incidents to the FBI, and its president Cecile Richards wrote to US Attorney General Eric Holder detailing the visits and outlining possible sex trafficking-related crimes that may have been committed.

"When Planned Parenthood learns of an operation that exploits young women, we vigilantly work with law enforcement authorities to uncover and stop this abhorrent activity," said Stuart Schear, a spokesman for Planned Parenthood, adding that the group has "been in contact with federal and local authorities to identify the persons involved in these visits."

The visits occurred between Jan. 11 and Jan. 15, to Planned Parenthood centers in New York, Washington, New Jersey, Indiana, Virginia, and Arizona, according to The Associated Press.

Although the identities of the visiting men were not revealed, Planned Parenthood suspected that they are linked to the fierce anti-abortion group Live Action, whose chief declined to confirm or deny to the AP any responsibility, but offered a strong hint that her organization was involved.

Live Action founder and president Lila Rose said Planned Parenthood's claims were "very interesting," but she added: "The story that speaks loudest will be in the evidence. I can't comment until we release the visual evidence."

Live Action has a history of targeting the abortion provider with undercover operations. It promised last year to "launch major investigations," to the tune of at least $125,000, into "the abortion industry" throughout 2011, mentioning Planned Parenthood three times in its press release.

The group said on its website that one of its goals involves "ending abortion, the greatest human rights injustice of our time."

Last year, a Live Action sting operation purported to reveal video evidence that Planned Parenthood was ignoring evidence of statutory rape, an allegation the reproductive rights group disputed.

Conservative blogger Michelle Malkin hailed Live Action's "invaluable investigative work" in 2008. Right-wing media prankster James O'Keefe, known for similar undercover operations, had also targeted Planned Parenthood in the past.