Washington (CNN) Former CIA Director Michael Hayden anticipates many more indictments -- including those of Americans -- to come in special counsel Robert Mueller's investigation into Russian interference in the 2016 US election.

Appearing on CNN's "The Lead with Jake Tapper" on Friday, Hayden expressed his belief that today's indictments against 12 Russian officers are not the end.

"The richer in detail we get, the more I begin to believe that we're probably going to be seeing a widening circle (of indictments) here," Hayden said.

Hayden, who was CIA director under President George W. Bush, added that he "would not be surprised" if future indictments were of Americans, citing the seemingly deliberate move to not explicitly deny American involvement in today's indictment.

"The indictment clearly says, we take no view on whether Americans were involved," he explained. "It doesn't say there were no Americans involved."