(CBS News) - CBS News has learned the names of two of the Secret Service agents being ousted from the agency for alleged inappropriate behavior involving prostitutes on a presidential mission to Cartagena, Colombia. U.S. government investigators are now on the ground in Cartagena trying to piece together what happened last Wednesday night. Investigators have the names of all the women involved and none are believed to be underage. The youngest woman was 20 years old. According a congressional staffer, one agent involved in an altercation with a prostitute over payment did not realize there was payment involved or that the woman was a prostitute. One woman, an escort, spoke out to The New York Times about the incident. CBS News has also learned that all agents accused of wrongdoing are undergoing drug testing, but there is no evidence of drug use and that polygraphs have been conducted on agents involved all week. As Secret Service officials continued to brief lawmakers, there was widespread outrage on Capitol Hill Thursday. Former House Speaker Nancy Pelosi called the conduct "disgusting" and said it's time for the Secret Service to clean house. Pelosi: Secret Service scandal "disgusting" "I don't see how those who are involved in this should be able to continue in their work," she said. The Secret Service is being careful not to stay that such behavior has never happened before, but officials have told congressional investigators that a similar incident has never been reported to the Office of Personal Responsibility.