One source said the agency has been subjecting operatives working in Libya to frequent polygraph tests to make sure they are not leaking information about Benghazi, the cable news channel reported Thursday.
Three other U.S. citizens were killed with Stevens in the attack on the consulate on Sept. 11, 2012. The attack became a political football with Republicans accusing President Obama and Secretary of State Hillary Clinton of a coverup.
Sources told CNN the CIA used an annex to the consulate as its local headquarters and at least 22 people were there the night of the attack. One source told CNN a total of 35 people were at the consulate and the annex with seven of them wounded.
Robert Baer, a former CIA agent who serves as a CNN analyst, said under normal circumstances the agency only puts its employees through polygraph tests every three or four years.
"If somebody is being polygraphed every month, or every two months it's called an issue polygraph, and that means that the polygraph division suspects something, or they're looking for something, or they're on a fishing expedition. But it's absolutely not routine at all to be polygraphed monthly, or bimonthly," Baer said.