Updated

Sen. Susan Collins is asking the White House for more information about the Colombia prostitution scandal after the lead federal investigator said White House personnel may have been involved.

In a letter sent to the White House Counsel Kathryn Ruemmler on Friday, the top Republican on the Senate Homeland Security and Governmental Affairs Committee wrote:

"While the (Secret Service), Department of Defense, Department of Justice, and Drug Enforcement Agency have all investigated the actions of their personnel in Cartagena and made the results of those investigations available to the Committee, to date the Administration has not explained the apparent inconsistency between its investigation and the findings of the DHS OIG."

Collins was referencing a Sept. 22 letter to Collins' committee from Department of Homeland Security Acting Inspector General Charles Edwards. He wrote that his office's investigation found "a hotel registry that suggests that two (non-Secret Service) personnel may have had contact with foreign nationals."

One of those employees, Edwards wrote, was a Defense Department employee "affiliated" with the White House Communication Agency.

The other, he said, "may have been" affiliated with the White House advance team. The White House, though, denied wrongdoing on the part of that team member.

The letter came two days after a FoxNews.com report revealed possible White House advance team involvement.

In the letter sent to White House counsel on Friday, Collins quoted the IG's letter, saying: "These findings appear at odds with a statement made on April 23 by the White House spokesman."

Collins was referencing Press Secretary Jay Carney's claim at the time that there were "no specific, credible allegations of misconduct" and that a review "came to the conclusion that there's no indication that any member of the White House advance team engaged in any improper conduct or behavior."

Collins is now asking:

"At the time of the incidents, what positions did these two individuals occupy on the White House or White House-affiliated staffs (including but not limited to the advance team or the White House Communications Agency, and including paid or volunteer positions)?"

Additional questions directed to White House counsel include details on these two individuals' job duties, what office they were working for on the Cartagena trip and the names of their supervisors.

Collins also asked for descriptions of the incidents they were allegedly involved in, and the findings and outcome of any investigation into those incidents.

Collins asked for a response from the White House by Oct. 9.

In response to the inspector general's letter to Collins on Sept. 22, the White House said the person mentioned as a possible member of the White House advance team was an unpaid volunteer who was not on the White House staff. An administration official also said the volunteer was wrongly implicated based on inaccurate hotel records.

Contact Jana Winter at jana.winter@foxnews.com