The CIA allegedly had “dozens” of agency operatives on the ground at the U.S. Consulate in Benghazi during last year’s deadly terrorist attack that ended with the deaths of Ambassador Chris Stevens and four other Americans.

Langley is taking extreme measures to mask the agency’s operations in Benghazi and in northern Libya at the time of the strike, according to CNN.

Agency employees involved with CIA operations in the country are being subjected to monthly polygraph tests, among other counterintelligence measures, an unnamed source told CNN.