TMZ has learned one of Maroney's attorneys fired off a letter to P0rn.com ... informing the site that McKayla was underage in several of the photos. The letter demands the images of McKayla -- who turned 18 last December -- be taken down immediately.
Another attorney for the gymnast sent a different letter to multiple websites stating Maroney owns the copyright on the hacked photos.
The legal claims by her attorneys are a strong indication the photos really do show McKayla -- even though she said on Twitter they were "fake photos." It's also possible only portions of the images are really McKayla. The letter is not specific.
A rep for P0rn. com tells us they immediately removed the pics once they got the letter from Maroney's attorney.
