By Michael Isikoff and Libby Leist, NBC News
Updated at 6:27 p.m. ET: Three Secret Service agents implicated in the scandal involving the procurement of women during President Barack Obama's trip to Colombia are leaving the agency, a spokesman said Wednesday.
In a statement, the spokesman, Paul Morrissey, said a supervisory employee was allowed to retire, a second supervisory employee was listed for "removal for cause" and a non-supervisory employee had resigned.
Eight other agency employees remain on administrative leave without their security clearances, Morrissey said.
The statement confirmed a report earlier Wednesday by NBC News that the implicated agents were "offered" the opportunity to submit to polygraph tests. A U.S. official told NBC News that some of them had agreed.
New details of the scandal emerged after a round of congressional briefings Wednesday.
Eleven women were involved with 11 Secret Service personnel, a Senate source told NBC News. Investigators are looking into reports of drug use but haven't found any evidence yet, the source said.
None of the 11 men had guns, radios, equipment or schedules in their rooms, the source said, clarifying questions raised on Capitol Hill about whether operations or presidential security may have been compromised.
As a result of the scandal, the agency is undertaking a review of its policies regulating contact with foreign nationals, the source said.
"We demand that all of our employees adhere to the highest professional and ethical standards and are committed to a full review of this matter," the agency's statement said.
Michael Isikoff is NBC News' national investigative correspondent. Libby Leist is a producer for NBC News.
This is a developing story. Check back for updates.
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