Facebook CEO Mark Zuckerberg is facing growing bicameral, bipartisan calls for him to testify on Facebook's role in the collection of personal data of millions by Cambridge Analytica.

Sens. Ed Markey (D-Mass.) and Richard Blumenthal (D-Conn.) Thursday (March 22) said in a letter to the Facebook founder that they appreciated Zuckerberg's engagement on the issue.

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Those include:

• "What are Facebook’s policies, practices, and procedures for approving any applications that collected Facebook user data.

• "How has Facebook verified that the collected data is used solely for purposes provided by developers (including academic entities) and not improperly used or shared?

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• "Between 2007 and 2014, how many applications that accessed “friends data” did Facebook host? To your knowledge, did other applications misuse or fail to safeguard this data?

• "What is the extent of Facebook’s right to audit external applications that collect user data?

• "How many times has Facebook exercised its right to audit applications?"

They want answers by April 12 and want him to testify under oath at a hearing they have called for. In an interview with CNN, Zuckerberg said he would be happy to testify if it was the right thing to do.

Over in the House, Republican House Energy & Commerce Committee chairman Greg Waldenand ranking member Frank Pallone (D-N.J.) called on Zuckerberg to testify before their committee, echoing the lack of satisfactory answers to troubling questions.

“The latest revelations regarding Facebook’s use and security of user data raises many serious consumer protection concerns," they said. "After committee staff received a briefing yesterday from Facebook officials, we felt that many questions were left unanswered. Mr. Zuckerberg has stated that he would be willing to testify if he is the right person. We believe, as CEO of Facebook, he is the right witness to provide answers to the American people. We look forward to working with Facebook and Mr. Zuckerberg to determine a date and time in the near future for a hearing before this committee."

Cambridge Analytica used Facebook user data (from some 50 million users) to build profiles it then sold to political campaigns.

Facebook has suspended Cambridge for violating its policies, saying the company got the information from a third party, which it should not have been able to do.