American Media, the National Enquirer's parent company, was granted immunity last year in connection with its assistance on an investigation into Michael Cohen, President Donald Trump's former personal lawyer. That agreement required the company to agree to "commit no crimes whatsoever."

Federal prosecutors are reviewing the National Enquirer's handling of a story involving Jeff Bezos' affair, a source familiar with the matter told NBC News. Prosecutors are seeking to determine whether the tabloid violated an earlier immunity agreement.

In an extraordinary blog post published Thursday, Bezos detailed allegations of blackmail and extortion against the publisher. American Media could lose its immunity deal if Bezos' accusations are substantiated.

In the post, Bezos said that he "engaged investigators" to figure out how the National Enquirer obtained his text messages that it published in its story about his marital infidelity. "As it turns out, there are now several independent investigations looking into this matter," he wrote, somewhat cryptically.

Bezos is founder and CEO of Amazon and the owner of The Washington Post.

American Media said in a statement Friday that it believed it had "acted lawfully in the reporting of the story of Mr. Bezos." The company said it would look into the allegations and take "whatever appropriate action is necessary."

The U.S. Attorney's Office for the Southern District of New York declined to comment. The news of prosecutors' actions was first published by Bloomberg News.