Top Republicans on the Senate Commerce Committee pressed Google's chief executive officer on Thursday to produce an internal memo that suggested the tech giant keep private its discovery that vulnerabilities in a social networking platform had exposed user information.

Google didn't disclose early this year a finding that private data from as many as 500,000 Google Plus users had been accessible to app developers out of concern about heightened regulatory scrutiny, according to the Wall Street Journal, which described a memo on the matter. Social media giant Facebook was facing a firestorm of criticism at the time over reports that a consultant to President Trump's 2016 campaign, Cambridge Analytica, had improperly gained access to information on 87 million of its users.

Senate Commerce Committee Chairman John Thune of South Dakota, along with Sens. Roger Wicker of Mississippi and Jerry Moran of Kansas, pressed CEO Sundar Pichai to say when the company became aware of the vulnerability and whether it informed agencies like the Federal Trade Commission.

“Improving transparency will be an essential pillar of the effort to restore Americans’ faith in the services they use," the lawmakers wrote in a letter to the CEO. "It is for this reason that the reported contents of Google’s internal memo are so troubling."

Google's disclosure came just weeks after its top privacy officer testified in front of the commerce panel. While data privacy was the topic of that hearing, the official didn't mention the issues with Google Plus, a service the company plans to stop offering to consumers.

The Commerce Committee is seeking to advance legislation to launch the nation's first privacy framework, though no bill is expected prior to the 2018 midterm elections.