Senate Judiciary Chairman Chuck Grassley, R-Iowa, is pressing Google for answers on what future actions will be taken to safeguard personal information from its users, after Google failed to disclose this year that app developers could access private data from thousands of Google Plus users.

“I write with regard to recent troubling reports that Google exposed the private data of approximately 500,000 Google+ users and then failed to disclose the glitch, despite knowing about it since March,” Grassley wrote to Google CEO Sundar Pichai on Friday.

Grassley noted that Google had been invited to testify before the Senate Judiciary and Commerce committees in April, along with Facebook CEO Mark Zuckerberg and Twitter representatives, as part of a hearing on consumer data privacy on social media platforms.

At the time, it had been recently reported that Facebook shared user information with data firm Cambridge Analytica, which did not delete data it had improperly obtained from Facebook users.

However, Grassley noted that Google “declined to come before Congress and the American people, asserting that the problems surrounding Facebook and Cambridge Analytica did not involve Google.”

“Despite your contention that Google did not have the same data protection failures as Facebook, it appears from recent reports that Google+ had an almost identical feature to Facebook, which allowed third party developers to access information from users as well as private information of those users’ connections,” Grassley wrote. “Moreover, it appears that you were aware of this issue at the time I invited you to participate in the hearing and sent you the letter regarding Google’s policies.”

[More: Top senators dig into Google following its 'troubling' handling of user data exposure]

Grassley is seeking a response from Google by Oct. 26, addressing why it took three years to identify the glitch, what actions Google has taken to guarantee user data wasn’t used inappropriately by third-party developers, and if any audits of third-party developers have been conducted or will be conducted.

Additionally, he is seeking answers as to why users and members of Congress were not notified about the issue in March when Google first became aware of it, and whether Google can determine what information was collected.

On Thursday, Republicans on the Senate Commerce Committee requested Pichai answer similar questions, and also asked him to provide the committee with Google’s internal memo cited in the Wall Street Journal. The Journal was the first to report the glitch.

“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 Pichai Thursday. "It is for this reason that the reported contents of Google’s internal memo are so troubling."

Google did not immediately respond to a request for comment from the Washington Examiner.