Mark Zuckberberg is expected to testify before the Senate Judiciary Committee next month about the harvesting of data on 50 million users during campaign season, but one member of the panel said the Facebook CEO and related documents should be under subpoena.

Facebook announced mid-month that it hired a forensic analysis firm to delve into Cambridge Analytica, a data mining firm that worked on President Trump’s campaign, after reports that the company held onto user data that had been improperly harvested.

Paul Grewal, VP and deputy general counsel for Facebook, said in a statement posted Friday on the company’s website that Cambridge Analytica had been suspended from Facebook and they were “moving aggressively to determine the accuracy” of claims that the political data firm didn’t delete user info “contrary to the certifications we were given.”

In a detailed interview with the Guardian, Christopher Wylie, the whistleblower who conceived the joining of political research and psychological targeting that started Cambridge Analytica (Steve Bannon was on the firm’s board), said Facebook lawyers didn’t reach out to him until August 2016 to demand that “illicitly obtained” data be deleted. “Literally all I had to do was tick a box and sign it and send it back, and that was it,” says Wylie. “Facebook made zero effort to get the data back.”

The UK and EU have launched investigations into Cambridge Analytica.

Senate Judiciary Committee Chairman Chuck Grassley (R-Iowa) invited Zuckerberg to testify at an April 10 on data privacy; Google CEO Sundar Pichai and Twitter CEO Jack Dorsey have also been invited. Other committees have also requested a session with Zuckerberg.

Sen. Richard Blumenthal (D-Conn.), who sits on the Judiciary Committee, told CNN today that “there ought to be subpoenas for him in case he changes his mind, for documents that Facebook has and for Cambridge Analytica and Aleksandr Kogan who are key, also, to knowing how this information on 50 million people was harvested and then abused, illegally juiced to mine and manipulate other data.”

Kogan is a psychology professor at the University of Cambridge who gathered users’ data through an app that promised to predict the Facebook user’s personality. Facebook says about 270,000 people downloaded the app and Kogan “violated our platform policies” by passing the collected data over to Cambridge Analytica.

“Facebook has a problem with truth and with trust. It needs to tell the truth to Congress about whether it knew. It says that in 2015, it asked all this data be deleted, and it never verified it. It never, very alarmingly, told the users that their data was out there potentially at risk. That is deeply concerning,” Blumenthal said. “I think that the Facebook attitude, quite frankly, has been, trust us, we know better.”

“Their business model is to sell information about you and me without our knowledge or consent. They need to accept rules that require knowledge, full disclosure and consent, not only when that information is initially sold or shared, but also when it is used afterward. And they need to devise rules to protect the information from breaches.”

The senator said he “wouldn’t advise people on whether they should delete their accounts.”

Rep. Sheila Jackson Lee (D-Texas) told Bloomberg News on Tuesday that she asked Zuckerberg to come before the House Judiciary Committee “because we have a regulatory authority over the FTC, we have concerns and jurisdiction over the issues of privacy, the issues of freedom of speech, but also the issues of due process.”

“We need the hearings to be fact-finders to write the right kind of regulatory scheme to ensure that the business element of Facebook continues,” she said. “We have no desire to undermine the business element or the consumers, but we do have a responsibility, constitutional responsibility, to protect the American people from invasion of their privacy without their knowledge and without compensation.”