Political pressure mounting on FBI

Henry: Critical that FBI be expeditious with findings

With the election just days away, it's "critical" that the FBI release anything it has found in its investigation into newly discovered emails related to Hillary Clinton, former Executive Assistant FBI Director Shawn Henry told CNBC on Thursday.

The FBI announced last Friday that it was looking into emails reportedly discovered during a probe in which the devices of former Rep. Anthony Weiner and Clinton aide Huma Abedin were seized.

"Just merely that there's an ongoing investigation implies that there's something improper and that's completely against FBI protocol to talk about an ongoing criminal investigation. So to resolve that I think they need to come forward," Henry said in an interview with "Power Lunch."

That means even if the investigation is incomplete, because otherwise there is a big void heading into the election Nov. 8, he added.

"The vast majority of the American public, I think, sees something like that and they don't understand the totality of it. And I think it's important to fill the gap with the facts rather than leaving people to their own device to determine what that actually means," said Henry, who is now president of the cybersecurity firm CrowdStrike Services.

His company was hired by the Democratic National Committee to investigate and stop the hacking attacks on its computer network last June.

FBI's political pressure

Henry's comments come at a time when political pressure is mounting on the FBI about the Clinton emails and other possible investigations.

Eric O'Neill, a former FBI operative, told CNBC, "There can always be squabbles inside the family, but the dirty laundry is rarely laundered outside the FBI. And that's why this is so unusual."

As for how the Clinton email investigation will proceed, Henry said agents and analysts familiar with the case will use sophisticated technology and will do things like keyword searches and look for specific emails.

"They'll be looking for particular cases that they may have seen previously, top secret classification codes. They may be looking for certain numbers relating to certain documents," Henry noted.

— CNBC's Eamon Javers contributed to this report.