Wednesday morning, the Oversight Committee's chairman, Rep. Trey Gowdy, R-S.C., sent both White House chief of staff John Kelly and FBI Director Christopher Wray letters asking for details about the security background check of Porter, and the decision to keep him on the job before he quit last week.

"If a person committing domestic violence gets into government, then there's a breakdown in the system," Ryan said. "There's a breakdown in the vetting system and that breakdown needs to be addressed."

House Speaker Paul Ryan , R-Wis., told reporters Wednesday that the White House "clearly" has "work to do to fix their vetting system."

The probe comes as the White House, more than a week into the scandal, has continued to offer shifting explanations of the circumstances of Porter's now terminated tenure as a top aide to President Donald Trump .

The House Oversight Committee has opened an investigation into Rob Porter's White House employment while he was being accused of abusing his ex-wives.

Gowdy, in his letters, specifically asked for "the date on which any White House employee became aware of potential derogatory or disqualifying information on Porter from the date of his appointment to February 12, 2018, and which individual was notified."

Gowdy, during an appearance Wednesday on CNN's "New Day," revealed the Oversight Committee had opened the probe of Porter's employment Tuesday night — hours after Wray contradicted the White House's narrative about the case during an earlier appearance before a Senate committee.

"How do you have any job if you have credible allegations of domestic abuse? Again, I am biased toward the victim," Gowdy said on CNN, noting that he was "troubled by almost every aspect" of Porter's White House employment.

"I would want to know from [White House counsel] Don McGahn and General Kelly and anyone else: What did you know, from whom did you hear it, to what extent did you hear it and then what actions, if any, did you take?" Gowdy said. "The chronology is not favorable from the White House."

In a letter, Gowdy noted that Wray had told senators that the FBI's background investigation of Porter ended last year. White House representatives had been saying a background probe was still ongoing at the time of Porter's departure.

Porter, whose job required him to handle sensitive documents, was operating with a temporary security clearance at the time of his departure.

Gowdy's letter said his committee is investigating the policies and processes in which interim security clearances are handled within the executive branch, "and the extent to which any security clearance issued to Porter comported with those policies and processes."

Porter, 40, resigned as Trump's staff secretary a week ago after both of his ex-wives told U.K. tabloid the Daily Mail that he had physically and emotionally abused them during their respective marriages. Porter denies their claims.

Since he quit, the White House has failed to give reporters a consistent explanation of who in the administration knew about the women's allegations, when they knew it, why Porter was being allowed to operate with only a temporary security clearance and the timing of the decision that he should leave his job.

Both women had told the FBI about being abused by Porter when that agency was conducting a background check on him as part of the security clearance review process. Wray testified that the background investigation was completed last July, and that the FBI had earlier issued a preliminary report last March.

There have been multiple reports that top White House officials, including Kelly, knew for months that the women had or were prepared to make allegations against Porter, but kept him on the job despite that fact. White House spokesman Raj Shah, for his part, said last week that the administration could have handled the situation better.

On Tuesday, White House spokeswoman Sarah Huckabee Sanders claimed there was no contradiction between what the administration has been saying about Porter's case and what the FBI says.

Sanders said that the White House Personnel Office received the FBI's final report in November, but that the office had not finished its own investigation by the time Porter resigned. The office "had not made a final recommendation for adjudication to the White House because the process was still ongoing when Porter resigned," Sanders said.

Sanders' statement has done little to quell questions about why the White House kept Porter in his post, only to oust him last week once the women's allegations were made public.

Gowdy, in his letter, said he wanted to know whether the FBI played any role in adjudicating whether Porter should get an interim or final security clearance. He also wants to know the "security clearance adjudication dates for Porter, including both interim and final clearance."