Sister of Mel Gibson's ex under suspicion

THR exclusive: Sources close to the case say prosecutors are examining her role in the audiotape leaks

There finally might be an answer to the question of how the audio recordings of Mel Gibson and Oksana Grigorieva got posted online.

Several sources close to the case confirm that Oksana Grigorieva's younger sister, Natalie, is suspected of having leaked the audiotapes to and is being looked at by authorities.

"I suspect that if the authorities look at the sister, they'll find a wire transfer or a check to her from the website," a source said. "She and Oksana are very close."

Another source also claims that Oksana's sister was involved in shopping the tapes to media outlets before making the sale to Radar.

"All the tabloids said no to the deal because they were asked to purchase the audio tapes before hearing them," another source said.

If Natalie Grigorieva is found to have brokered the deal at the behest of her sister, it's possible the judge could find the Russian singer in contempt of court. The elder Grigorieva also could face extortion charges based on a text and e-mails she sent to Gibson.

In the text message, reported exclusively by THR on Wednesday, Oksana Grigorieva wrote Gibson that the reason she recorded him was that "you broke your agreement with me."

She claimed Thursday that the only reason she balked at signing the longform settlement agreement when it was placed in front of her was that it gave Gibson unsupervised visits with their child.

"The statement is completely false. This never happened," a source said, adding, "This is the third explanation that she's offered for why she backed out of the agreement."

In a custody hearing, Oksana Grigorieva's lawyer argued that she repudiated the agreement because she felt "coerced" and because she was "misadvised" by the retired judges overseeing the mediation.

Reps for Oksana Grigorieva and Gibson could not be reached for comment.