After a private briefing on the status of the Pentagon investigation into the the Secret Service  prostitution scandal, the two top lawmakers on the Senate Armed Services committee expressed disappointment over the slow pace of the investigation and a lack of concrete information to emerge.

Sen. John McCain, the ranking Republican on the committee, called today's update on Capitol Hill, delivered by Vice Admiral William Gortney, the director of the Joint Staff, a "very disappointing briefing" and "a waste of time," noting the dearth of concrete information about the scandal in which secret service agents and U.S. military personnel allegedly brought prostitutes back to their hotel rooms prior to President Barack Obama's arrival in Colombia for a summit with Latin American leaders.

McCain expressed frustration that despite the committee's obligation to conduct oversight on national security issues, there were few answers.

"They wouldn't even have information as to who was in charge on the ground in Cartagena. It was remarkable," McCain, R-Ariz., said incredulously. "There are clearly implications to national security when prostitutes were in these individuals' rooms. [The military personnel] have the schedules of the president's activity the following day.  We need that information. That's our duty to have that information and make decisions accordingly. This briefing today gave us no details on any aspect of it."

"Our obligation constitutionally," McCain added,  "is oversight of the activities of the men and women in the military and our national security. That's the job of the Senate Armed Services committee. Right now the Pentagon is being totally uncooperative in allowing us to fulfill those obligations."

Sen. Carl Levin, the chairman of the committee, was more subdued, telling reporters that he thought the briefing was "sketchy" but he also explained that "it was a preliminary briefing because the [Pentagon's] investigation is not completed."

"The military is traditionally reluctant to provide details of an investigation before it's completed because of their fear of undo command influence and the fear of prejudicing proceedings that might be carried out under the uniform code of military justice," Levin, D-Mich., said. "I was surprised that it was not fuller, but they gave us the reasons for why they proceeded this way, and that's where we're at."

The Pentagon did not comment after today's briefing.

Since the scandal broke on April 13, the Secret Service has moved quickly to investigate its officers. Already, 12 agents either have been cleared of serious misconduct, have resigned, retired, or been notified of personnel actions to permanently revoke their security clearances. Some agents could face firing for cause.

Levin said he was told that the Pentagon's investigation should be complete by the end of next week and he and McCain are expecting a comprehensive update the following week.

"[The Pentagon is] going to see whether or not that investigation leads to others, including they look up the chain of command to see whether or not there was any failure up the chain of command, either in the preparation for the summit or in the way in which the problem was handled," Levin said.

Despite their frustration with the flow of information in the briefing, Levin said he was able to learn two details from the investigation, including that there were curfew violations before the president arrived in Colombia and also that much of the U.S. military's mission there "was also to secure the entire area for this summit meeting at the request of the government of Colombia."

"There were curfew violations apparently by at least some of the 12 members of the military prior to the arrival of the president, but the decision was made nonetheless to let those folks, those members of the military, continue with the mission," Levin said. "That's a question which we obviously will be raising with the South Comm commander who apparently made that decision. That may have been the right decision, but it nonetheless raises an interesting question…whether that was an appropriate decision to let them continue on the mission given the seriousness of the mission, which of course is the security of the president."