CIA 'clamping down on Benghazi operatives' Around 35 Americans, most of them working for the CIA, are believed to have been in Benghazi on the night that Islamist militants killed Ambassador Chris Stevens and three others, CNN reported. The network said the CIA operatives were being routinely questioned by superiors, although it was not clear when the monthly interrogations began or what they focused on. Aki Peritz, a former CIA counter-terrorism analyst, said that operatives normally faced polygraph tests before they joined the agency and then every three to five years after that. "To put people through monthly polygraph tests is completely out of the ordinary," Mr Pertiz told the Daily Telegraph. It's either a fishing expedition or they are looking for something very, very specific. Mr Pertiz said he thought it was likely that tests were intended to stop the operatives from leaking to either Republicans in Congress or to the media about the Benghazi attack. "The CIA trades in secrets and in the shadows and when this stuff is in the press - and a lot is distorted for partisan reasons - it is infuriating for the entire agency," he said. The CIA said in a statement that its staff were "always free to speak to Congress if they want" but did not specifically deny the polygraph reports. "We are not aware of any CIA employee who has experienced retaliation, including any non-routine security procedures, or who has been prevented from sharing a concern with Congress about the Benghazi incident," the agency said. Nearly a year after the Benghazi attack on September 11, 2012, neither Libya nor the US has caught any of the perpetrators of the attack. Senator Lindsey Graham and seven other Republicans this week wrote to James Comey, the new director of the FBI, urging him to take a more aggressive approach to finding the killers. We appear to be no closer to knowing who was responsible today than we were in the early weeks following the attack. This is simply unacceptable," the Republicans wrote.