Greg Mortenson, author of the bestseller “Three Cups of Tea,” was sued for fraud on Friday in a class-action case accusing him of fabricating much of his story to promote the book and his Montana-based charity.

The lawsuit comes nearly four weeks after Mortenson and his Central Asia Institute (CAI) came under fire in an expose aired on the CBS television news program “60 Minutes,” which sparked an investigation by the Montana attorney general.

The “60 Minutes” report challenged the credibility of biographical details in Mortenson’s memoir and said his institute, founded to build schools for girls in Afghanistan and Pakistan, was largely being used to promote the book.

In particular, the “60 Minutes” report disputed his account of being kidnapped in Pakistan’s Waziristan region in 1996.

The book chronicles Mortenson’s unsuccessful attempt to climb the mountain K2 in South Asia and his encounter with impoverished Pakistani villagers whom he said inspired him to build schools and other projects in the region.

The lawsuit does not mention the CBS broadcast or give examples of purported fabrications. Nor does it say on what basis two named plaintiffs — Jean Price of Great Falls, Montana, and Michele Reinhart of Missoula — concluded that Mortenson was untruthful.

It said Price and Reinhart both bought copies of “Three Cups” and donated to CAI, relying on the veracity of statements Mortenson made in public speaking engagements they attended.

Mortenson’s publisher, Viking Press, has said that it, too, is reviewing claims that parts of “Three Cups of Tea” were concocted. Viking representatives could not be reached for comment on Friday.

But in a lengthy question-and-answer interview with Outside Magazine posted on CAI’s website, Mortenson defends his book and the institute’s work.

He acknowledged that the book, co-authored by David Oliver, contains “discrepancies” that result from “omissions and compressions” done for the sake of literary expediency. “But I’m not a journalist. I don’t take a lot of notes,” he said.

He insisted the abduction story was “pretty much” true, recounting, “I was definitely detained against my will,” though he said his captors never called themselves Taliban.

As for the institute’s finances, Mortenson conceded, “I am not a good manager,” and he said he hired a law firm to conduct a thorough audit when problems first surfaced and is implementing changes recommended by the firm.

He acknowledged that less than half of CAI’s proceeds have gone into building schools but said “much of the remainder was spent on CAI’s other charitable programs.”

He also said that a trusted intermediary the institute hired years ago to help get schools built overseas was later found to have been corrupt.

The lawsuit, filed in U.S. District Court in Missoula, Montana, claimed CAI “expended significant sums to finance Mortenson’s book tours and public speaking engagements.”

“During these activities, Mortenson and CAI have repeatedly fabricated material details about his activities and work in Pakistan and Afghanistan, including specific fabrications” in his book,” the suit claimed, adding: “The purpose of these fabrications was to induce unsuspecting individuals to purchase his books and to donate to CAI.”

The suit seeks a court order establishing a trust and assigning another existing charity to control the funds raised by CAI and Mortenson in order to construct schools they “claim to have built but did not build.”

“Three Cups of Tea” is a New York Times bestseller that has sold over 4 million copies, according to a biography on the website of his charity.