Secret Service scandal: Watchdog planning separate probe (Win McNamee - GETTY IMAGES) The top watchdog at the Department of Homeland Security told lawmakers Monday that he plans to launch a separate probe into the U.S. Secret Service sex scandal in Colombia after keeping close tabs on the agency's ongoing internal investigation for the last three weeks. Acting Inspector General Charles K. Edwards informed congressional offices Monday that he has launched an investigation to determine how well the Secret Service responded to the April 12 incident in Cartagena, Colombia. Edwards said his probe also will focus on the conclusions reached by the agency's separate investigation, the sufficiency of the disciplinary actions taken against personnel involved and how effectively the Secret Service is handling issues of diversity, recruitment and discipline. The Secret Service is one of more than 20 agencies and offices that comprise DHS. In a message sent Monday, Edwards sought to assure lawmakers that he has been kept abreast of the agency's ongoing investigation, noting that Secret Service Director Mark Sullivan first informed him of the incident on April 13, the day after agency officials identified an initial 11 personnel to be sent home from Colombia. Edwards said his office "determined that the USSS was best positioned to immediately initiate the investigation with the full understanding that they would keep OIG [Office of Inspector General] informed as the investigation progressed," according to Edwards's letter. We have maintained close contact with the USSS, coordinating with them as their internal investigation continued. During the past two weeks the USSS has been completely transparent and forthcoming with specific details and findings of their investigation. Edwards's decision to further investigate the situation should meet the demands of Republican lawmakers who requested a separate, independent probe to determine what occurred in Colombia before President Obama arrived for the Summit of the Americas, and whether what unfolded was an aberration or part of a larger cultural pattern at the Secret Service. Sen. Susan Collins (R-Maine) said Monday evening that while she maintains confidence in Sullivan and his ongoing investigation, "It is always difficult for an organization to investigate and reform itself, which is why the IG's involvement is so important." Collins is the ranking Republican on the Senate Homeland Security Governmental Affairs Committee, which is also investigating the matter, in addition to at least three other congressional committees. The Secret Service is due to deliver its initial findings on the Colombia scandal on Tuesday to the House Oversight and Homeland Security committees. Share your thoughts in the comments section below. Follow Ed O'Keefe on Twitter: @edatpost More from PostPolitics: Touting bin Laden killing seen as risky Is gridlock all the GOP's fault?