Ed Henry joined Maria Bartiromo this morning to discuss Tuesday's compelling back-and-forth with Hillary Clinton over her private email server.

At a Clinton campaign event in Las Vegas, Henry challenged Clinton on whether she "wiped her server clean."

Clinton joked back, "What, like with a cloth or something? I don’t know how it works at all."

She insisted that what she did with the private emails was all "legally permitted."

“Look, Ed, I take responsibility,” she said. “In retrospect, this didn't turn out to be convenient at all and I regret that this has become such a cause celebre. But that does not change the facts. The facts are stubborn – what I did was legally permitted.”

Henry said for the second time this week, Clinton appeared to be "making a joke" about the email controversy and trying to dismiss it as a serious issue.

Meantime, Fox News has learned that two emails about Benghazi led to the FBI investigation of Clinton's private email server.

Henry said it's unclear at this time why those messages triggered the probe.

He recalled that Clinton insisted months ago that the server contained no classified information. Henry said we now know that was not true. 

Clinton later clarified that any classified information in the emails had been labeled "classified" after the fact.