Secret Service agents and members of the U.S. military brought as many as 21 women back to their hotel during their assignment to Colombia last week, a top senator briefed on the prostitution scandal said Tuesday.

With 11 Secret Service agents and 10 military servicemembers allegedly involved, the account raises the possibility that everyone accused of misconduct could have tried to sneak women back to their rooms.

Sen. Susan Collins, R-Maine, the top Republican on the Senate homeland security committee, revealed the details after she was briefed for a half-hour Monday night by Secret Service Director Mark Sullivan. Collins said she learned that U.S. Marines, as well as the 11 Secret Service agents now on administrative leave, were allegedly involved.