Senator: Colombia prostitution scandal probably not isolated incident May 23, 2012 -- Updated 1126 GMT (1926 HKT) Sen. Susan Collins: Circumstances "suggest an issue of culture" Collins will deliver her remarks at a Senate committee hearing Wednesday Secret Service director Mark Sullivan is set to testify (CNN) -- The incident involving U.S. Secret Service agents and members of the U.S. military allegedly hiring prostitutes before President Barack Obama visited Colombia was "almost certainly" not isolated, according to Sen. Susan Collins of Maine. Collins' comments come in an opening statement she plans to give Wednesday morning at a hearing of the Senate Homeland Security Committee. She is the ranking Republican on the panel. The director of the Secret Service, Mark Sullivan, is set to testify at the hearing. The committee is investigating the use of prostitutes by Secret Service agents in Colombia last month before Obama's visit -- one of four congressional committees looking into the incident. "This reckless behavior could easily have compromised individuals charged with the security of the president of the United States," Collins said in her statement. ..." The facts so far lead me to conclude that, while not at all representative of the majority of Secret Service personnel, this misconduct was almost certainly not an isolated incident. The incident involved roughly 20 alleged prostitutes and has resulted in the dismissal of nine Secret Service members. Three others were cleared of serious misconduct. Collins noted that "it is basic 'counterintelligence 101' that Secret Service personnel and others holding sensitive positions of trust in the U.S. government should avoid any situation that could provide a foreign intelligence or security service or criminal gangs with the means of exerting coercion or blackmail. Yet two of the primary means of entrapment -- sexual lures and alcohol -- were both present here in abundance. While preliminary findings are that no weapons or classified material was in the agents' rooms, those involved "could easily have been drugged or kidnapped, or had their liaisons with these foreign national used to blackmail them," she said. ..." They willingly made themselves potential targets not only for intelligence or security services, but also for groups like the FARC or drug cartels. Collins said that 12 agents comprise 8% of the male Secret Service personnel in-country, and 9% of those staying at Cartagena's Caribe Hotel at the time. "Contrary to the conventional story line, this was not simply a single, organized group that went out for a night on the town together," she said. These were individuals and small groups of two and three -- 11 individuals from the Caribe and one from the Hilton -- that went out at different times to different clubs, bars and brothels but who all ended up in similar circumstances. Two agents were married supervisors, she said -- "that surely sends a message to the rank and file that this kind of activity is tolerated on the road ... the circumstances suggest an issue of culture." Meanwhile, three Drug Enforcement Administration agents are under investigation for allegedly soliciting sex in Cartagena. One of them had a long-term relationship with a prostitute, two government sources familiar with the investigation said. Investigations focus on agents' activities, relationships in Colombia The DEA agents were not involved in security for the president's trip, the government sources said. The DEA agent's relationship with the prostitute came to light after a Secret Service agent voluntarily reported to his superiors that he was at a party at the agents' Cartagena apartment on April 13 where the three agents and several women were present, the government sources said. The Secret Service agent is the 13th employee to be caught up in the Colombia scandal. He is on administrative leave, according to several sources, but is not expected to lose his job because he came forward on his own to report the incident. CNN's Ted Barrett, Kate Bolduan and Dana Bash contributed to this report.