Colombian prostitutes or Russian spies? 

GOP Sen. Charles Grassley posed the seemingly hypothetical question Tuesday as he continued to press for more details about the Colombia prostitution scandal that has rocked the Secret Service and U.S. military. 

Grassley, ranking member of the Senate Judiciary Committee, again raised the concern that U.S. agents could have exposed themselves to a spy-world honeypot scheme -- though there is no indication that the women involved in Colombia were working for any foreign government. 

"We're looking at something that is very, very serious when national security might not be protected properly," Grassley told RadioIowa. "Who knows who might be using prostitutes? The Russians are famous for that to get information out of us. You want to know that the president is protected." 

The Iowa senator has also raised doubts about the internal review at the White House that apparently cleared all White House staff of wrongdoing in the case. 

He told Fox News Tuesday he wants an inspector general or some other third party to retrace that review, questioning the "credibility" of the assessment conducted by the White House counsel. 

"Maybe they had a chance to talk to everybody, but it seems to me they came to that conclusion very quickly," Grassley said. 

On Wednesday morning, Homeland Security Secretary Janet Napolitano told the Senate committee the alleged April 11-12 incident posed "no risk" to President Obama, who arrived several days later for the Summit of the Americas. She also said she has not been informed about "any evidence that the president's team was involved."

Napolitano also said the Office of Inspector General is overseeing the agency's internal investigation and that she has no knowledge of similar incidents over the past 2 and 1/2 years.

White House Press Secretary Jay Carney has said there is no "credible" or "specific" allegation of misconduct by anyone on the White House advance team or staff. 

The Secret Service announced more disciplinary measures Tuesday evening, forcing out two more employees and permanently revoking the security clearance of a third. 

In addition, two other Secret Service employees were cleared of serious misconduct, which concludes the investigation of the agency employees so far identified in the scandal. 

In total, nine have been forced out or had their clearances stripped and three have been cleared of serious misconduct.