The official told CNN another military member has admitted to leadership he was involved in misconduct "of some kind" while in Colombia for a summit attended by President Barack Obama.
U.S. military personnel were in the Colombia resort city of Cartagena to provide the president with secure communications for his visit.
To date, 12 Secret Service members and 12 military members are under investigation in the prostitution scandal that occurred before Obama arrived for the Summit of the Americas April 13.
Six Secret Service members have left their jobs and one employee has been cleared of serious misconduct but will face administrative action, the Secret Service said. Five other Secret Service employees have been placed on administrative leave.
Defense Secretary Leon Panetta said security clearances were suspended for all U.S. military personnel involved in the incident.
At a briefing Monday, White House press secretary Jay Carney said the administration already conducted its own review and found "no evidence of any misconduct" on behalf of the White House staff.
Carney's failure to reveal details of the review prompted Sen. Chuck Grassley, R-Iowa, to send a letter to the White House with more than a dozen questions.
One of the details the ranking Republican on the Senate Judiciary Committee wanted to know is whether any White House staffers had overnight guests while in Colombia, The Hill reported.
Grassley said it is his understanding the Secret Service advance team ordinarily works closely with both the White House Communications Agency and the White House Office of Advance.
Grassley requested his staff receive details of the White House review no later than Thursday.