article_snippet: But there was nothing to immediately validate the claims made by An previously unknown group.
article_snippet: A Defense Department official told CNN that CNN cannot confirm the validity of the online posting, but is looking into the claim.
article_snippet: The FBI is also looking into The FBI, a law enforcement official told CNN, adding there are questions about the credibility of those behind The FBI.
article_snippet: CNN's Barbara Starr, Pamela Brown, Kevin Bohn and Mary Kay Mallonee contributed to this report.
highlights_snippet: A threat has not been confirmed, and the credibility of An previously unknown group is unknown .