Three more Secret Service Agents resign WASHINGTON (Reuters) - The U.S. Secret Service said on Friday that three more of its employees have resigned, bringing to six the number that have left the agency in connection with alleged misconduct involving prostitutes in Colombia last week before President Barack Obama's trip there. The Secret Service also said that a 12th employee had been implicated in the ongoing investigation into a night of partying on April 11-12 that embarrassed the United States and overshadowed Obama's participation in the Summit of the Americas last weekend. The agency's statement said that one employee had been cleared of "serious misconduct" but would face administrative action - presumably something short of losing his job. Eleven Secret Service agents were originally linked to the scandal last week in which at least 21 women were brought back to a beach front hotel in the coastal city of Cartagena, badly damaging the agency's clean-cut, security-conscious image. Two of the three Secret Service employees who left the agency earlier in the week, David Chaney and Greg Stokes, were supervisors. The Pentagon on Friday also increased by one the number of military personnel under investigation in the episode, saying it was 11 instead of 10 as previously reported. The 11th man was a member of the Army's Special Forces. The misconduct in Cartagena was exposed when one of the women complained that she was not paid enough, resulting in the local police getting involved. President Obama was briefed on the investigation on Friday in the Oval Office by Secret Service Director Mark Sullivan, a White House official said, but gave no details of the content. The Secret Service, part of the U.S. Department of Homeland Security, among other duties, is responsible for protecting the president, vice-president, former presidents, presidential candidates and their families, and foreign embassies. White House spokesman Jay Carney repeated on Friday that Obama had faith in the Secret Service. Obama, who arrived in Cartagena the day after the scandal erupted, also believed that his security was "never compromised" in Colombia, Carney said. The Secret Service said it was still investigating, "utilizing all investigative techniques available to our agency. This includes polygraph examinations, interviews with the employees involved, and witness interviews," the statement by Assistant Director Paul Morrissey 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," it said. The 12th Secret Service agent was implicated as the agency broadened its inquiry to examine the activities of every employee that had been in Cartagena last week, a U.S. government source said. "The U.S. Secret Service is now interviewing every agency employee who was in Colombia," the source said. Typically many Secret Service personnel as well as military support and advance teams from the White House are sent to a foreign destination to prepare for a presidential trip. The Secret Service group that was implicated in the scandal had arrived in Cartagena with the plane that brings the presidential vehicles, another government source said. The military service members under investigation include six Army Special Forces soldiers, two Marines, two members of the Navy, and one Air Force member, the spokesman for the United States Southern Command in Miami, Colonel Scott Malcolm, said in a statement. They had all returned to their parent commands, he said. He said the investigating officer and a military lawyer assisting him were still in Cartagena, but would probably return to the United States this weekend and interview those suspected of misconduct in person "straight away." Republican Senator Charles Grassley asked on Friday whether records of the overnight stays of members of the White House's advance team in Cartagena were also being reviewed. If not, why not? Grassley asked in the letter to Sullivan and the acting inspector general of the Department of Homeland Security, Charles Edwards. Additional reporting by Alister Bull, Missy Ryan and Phil Stewart; Editing by Stacey Joyce and Eric Walsh