The House Oversight Committee launched an investigation into the security clearance for former White House Staff Secretary Rob Porter on Wednesday, escalating a growing controversy into what the White House knew about domestic violence allegations against President Trump's senior aide.

Chairman Trey Gowdy, R-S.C., sent letters to White House Chief of Staff John Kelly and FBI Director Christopher Wray, demanding answers about who in the White House knew of the accusations by two ex-wives.

Porter, whose job as staff secretary gave him access to some of the most sensitive documents the president sees, was allowed to work on an interim security clearance until he resigned last week when the accusations came to light. Two of Porter's ex-wives accused him of physical abuse, and told FBI agents that he could be susceptible to blackmail.

"The committee is investigating the policies and processes by which interim security

clearances are investigated and adjudicated within the executive branch, and the extent to which any security clearance issued to Porter comported with those policies and processes," Gowdy said in the letters.

Gowdy pointed to conflicting accounts of the timeline of Porter's clearance from Wray, who testified to the Senate Tuesday that the background investigation was completed in July, and White House press secretary Sarah Huckabee Sanders, who said the process was "ongoing" and "hadn't been completed" when Porter left his job.

House Speaker Paul Ryan, R-Wis., said Wednesday that Gowdy was "doing his job" by looking into the process by which Porter was given an interim clearance.

"They clearly have work to do to fix their vetting system," he said. “There’s a break down in the system.”

Ryan also suggested that Trump should be more forceful in directly condemning abuse.

"I mean come on, clearly we should all be condemning domestic violence," he said.