An investigation for the agency that oversees the U.S. Secret Service suggests Director Mark Sullivan lied during his congressional testimony in the Colombia prostitution scandal that ensnared 13 of his agents, multiple law enforcement officials and congressional sources tell FoxNews.com.

Investigators with the Department of Homeland Security's Office of Inspector General (DHS OIG) have completed their investigative report, which will be referred to the Department of Justice along with a memorandum of activity that lists potential criminal actions. The report indicates Sullivan may have obstructed Congress by lying about the criminal associations of prostitutes involved in the scandal. The report also alleges Sullivan may have manipulated a report requested by the Senate Homeland Security and Governmental Affairs Committee, the sources said.

DHS OIG uncovered the evidence -- including specific incidents of alleged perjury, making false statements and impeding Congress -- during its ongoing probe into the scandal surrounding agents' misconduct prior to President Obama's trip to Cartagena, Colombia, last April, sources told FoxNews.com. Sources said Sullivan may have violated statute 18 USC § 1505 -- obstruction of proceedings before departments, agencies and committees -- and investigators are now handing the case over to federal prosecutors in the Justice Department's Public Integrity Section.

DHS OIG has been in talks with Justice Department prosecutors in the Public Integrity Section for months, and met with them late last week about the potential charges against Sullivan, sources said.

The OIG, however, declined to discuss details of its investigation.

"The Department of Homeland Security Office of Inspector General is conducting an ongoing investigation, requested by Congress, of the United States Secret Service regarding its actions during a presidential visit to Cartagena, Colombia, earlier this year," Charles Edwards, acting inspector general, said in a written statement. "The department and the Secret Service have cooperated with the OIG’s investigation thus far. However, as a matter of policy, the OIG does not discuss its ongoing investigations."

Sullivan has retained private counsel in the case. Joshua Hochberg, a former DOJ Public Integrity Section deputy chief-turned-white-collar defense attorney, specializes in defending public officials and CEOs charged with corruption. Hochberg was with Sullivan at his Aug. 2 interview with DHS OIG investigators, sources said. Hochberg also led the DOJ investigation of the failed energy company Enron and was head of DOJ's Fraud unit before joining a private firm.

Reached for comment, Hochberg denied the allegations.

"I've confirmed the public integrity section at DOJ does not have an open investigation. Mr. Sullivan did not in any way obstruct Congress," Hochberg told FoxNews.com.

Sources said DOJ may not yet have an official open case on Sullivan because DHS OIG has not completed handing over a final report. The Justice Department will decide if the case will be prosecuted only after evaluating the DHS OIG report.

Multiple sources tell FoxNews.com that DHS OIG officials have been in talks with Justice Department officials for months about the possible charges against Sullivan. DHS OIG also notified the FBI, as is protocol, when it uncovered evidence early on in the investigation that Sullivan may have violated federal law.

Secret Service spokesman Ed Donovan, in response to inquiries from FoxNews.com, defended the agency's handling of the Colombia probe.

"Director Mark Sullivan and the Secret Service have conducted a fair and thorough investigation resulting from the Cartagena incident. The agency response to those with oversight responsibility has been timely and truthful. We will continue to respond to the DHS-OIG and congressional inquiries in that manner," Donovan said in a statement. "We will not respond specifically to anonymous allegations that have lingered since the beginning of this investigation that are either without merit, grossly inaccurate or blatantly false."

During the May 23 hearing before the Senate committee, Sen. Susan Collins, R-Maine, asked Sullivan: "Have you now been able to definitively conclude that the women were not associated with -- that they were not foreign agents? That they did not work for drug cartels? That they were not involved in human trafficking? That they were not working for FARC, for example, or other terrorist groups?"

Sullivan replied: "One of the first things we did, Senator, was to get the names of all the women. We had their country identification number. We provided those names and identifiers to some of our various partners out there who could verify for us if there was any connection with any type of criminal activity or criminal organization as well as any type of intelligence concerns that we may have.

"All of the information that we have received back has concluded that there was no connection either from a counterintelligence perspective or a criminal perspective."

Multiple high-ranking law enforcement officials close to the investigation told FoxNews.com that at the time of his testimony, Sullivan knew the intelligence community had found one confirmed hit -- meaning one of the prostitutes hired by a member of the Secret Service showed up in a CIA database of known criminals -- and one partial, unconfirmed, hit.

A search of the names of the prostitutes in a CIA database came back with a hit, which was confirmed before the May 23 hearing.

"He lied, absolutely he lied to Congress. He knew it, he knew what he was saying was a lie," said a law enforcement official close to the investigation.

"One hit was the CIA hit, the prostitute in question was tied to a drug cartel for laundering money," a law enforcement official close to the investigation told FoxNews.com.

"Sullivan had direct evidence of the hit," the source said.

"The night before his May 23 testimony before the Homeland Committee, he knew but he lied and said there was no hit and nothing was compromised."

At the time of his testimony, sources say Sullivan also knew of a partial hit, meaning a name in an intelligence database matched the name of one of the women who were checked into a Cartagena hotel by a member of the Secret Service. Investigators later determined after the May 23 hearing that the prostitute signed in by the Secret Service agent was not the same woman found to have ties to a criminal group, but simply shared the same name. But sources said at the time Sullivan testified before Congress he knew there was a potential second hit on a second prostitute that was still in the process of being confirmed, and therefore lied about this second possible association. It was only after the hearing that they learned the partial hit was ruled out.

Sources said Sullivan could not have known when he testified if this partial hit could be confirmed or ruled out.

These investigative findings are part of DHS OIG's ongoing and wide-ranging probe into the overall culture of Secret Service to DOJ prosecutors. The full report is not expected to be released for months.

In addition to his alleged perjury, Sullivan is suspected of misleading Congress in his responses to written questions for the record submitted by lawmakers, including Rep. Peter King of the House Homeland Security Committee.

Other potential charges stem from allegations that Sullivan conspired with his top deputies to manipulate, falsify or edit records to downplay past problems in a report compiled for the Senate Homeland Security Committee, which requested a report on the agency's last three years of disciplinary actions taken against its employees.

The report was referenced several times during the May 23 hearing.

Multiple high-ranking officials within the Secret Service said Sullivan and other top Secret Service officials also conspired to manipulate other internal investigations, including a probe into whether members of the Secret Service had hired prostitutes before a March 2011 presidential trip to El Salvador. The investigation was ordered after a news report from South America alleged that Secret Service agents had hired prostitutes and visited strip clubs in advance of President Obama's visit.

But a recently retired senior executive with Secret Service shot down these allegations, and defended Sullivan, his longtime friend and colleague. He also said Sullivan would never lie, let alone commit perjury before Congress.

"I don't know anyone who is more honest, more trustworthy, with more of a conscience than Mark," said the recently retired senior executive. "Mark Sullivan is an altar boy."

The retired official also said the internal El Salvador investigation uncovered absolutely no wrongdoing on the part of the Secret Service.

"No one in the history of the Secret Service has ever gotten a prostitute before Colombia," he insisted.

Sullivan was appointed director of the Secret Service in May 2006. The Arlington, Mass., native began his career with the agency in 1983 as a special agent in the Detroit Field Office. During his 28 years with the agency, he has served as deputy assistant director in the Office of Protective Operations; deputy special agent in charge of the Vice Presidential Protective Division and deputy assistant director, Office of Human Resources and Training.

The Cartagena prostitution scandal isn't Sullivan's first. In December 2009, he was called to testify before Congress about security failings that allowed uninvited guests Tareq and Michaele Salahi to crash an official state dinner at the White House. Sullivan took responsibility for the breach, saying: "This is our fault and our fault alone."

Email this reporter at Jana.Winter@FoxNews.com.