A Facebook spokesman confirmed to ABC News that the company received the invitation to appear on April 10, moments before it was shared with the media, and said that it was being “reviewed.”

This comes as the Federal Trade Commission – earlier Monday - announced it had opened its own investigation looking into whether or not the tech giant violated a 2011 consent decree it signed promising to protect users’ privacy.

“Companies who have settled previous FTC actions must also comply with FTC order provisions imposing privacy and data security requirements,” the agency wrote in a press release. “Accordingly, the FTC takes very seriously recent press reports raising substantial concerns about the privacy practices of Facebook. Today, the FTC is confirming that it has an open non-public investigation into these practices.”

Facebook Deputy Chief Privacy Officer Rob Sherman said last week of rumors of the FTC action, “We remain strongly committed to protecting people’s information. We appreciate the opportunity to answer questions the FTC may have.”

The controversy has roiled company stock, and the announcement Monday of the federal agency probe sent the company’s stock sliding even further, down nearly four points at its lowest midday trading point.

Cambridge Analytica has previously said it was unaware the data was improperly obtained by a third party, and the firm says it cooperated with Facebook in deleting all the social media company’s data and related information in 2015. Such material was not utilized as part of its work with the 2016 Trump presidential campaign, the data firm said.

The Trump campaign has said it never used data from Cambridge Analytica. The Judiciary Committee, for its part, said it plans to cover “privacy standards for the collection, retention and dissemination of consumer data for commercial use. It will also examine how such data may be misused or improperly transferred and what steps companies like Facebook can take to better protect personal information of users and ensure more transparency in the process.”

Grassley also invited Google CEO Sundar Pichai and Twitter CEO Jack Dorsey to discuss mounting privacy concerns and “how to develop ‘rules of the road’ that encourage companies to develop tailored approaches to privacy that satisfy consumer expectations while maintaining incentives for innovation.”

Pressure is building for Zuckerberg, in particular, to face what will surely be a series of public grillings, as the list of congressional panels demanding his appearance grows.

Already, the embattled billionaire businessman has received requests from the Senate Commerce Committee and the House Energy and Commerce Committee, and the Senate Select Committee on Intelligence has said it intends to extend an invite, as its panel continues its more than 14-month long investigation into Russian interference in the 2016 presidential election.

There are also international demands for Zuckerberg to appear before government panels in the UK, Australia, and beyond.

“On a bipartisan basis, we believe Mr. Zuckerberg’s testimony is necessary to gain a better understanding of how the company plans to restore lost trust, safeguard users’ data, and end a troubling series of belated responses to serious problems,” Sens. John Thune, R-S.D., and Bill Nelson, D-Fla., the chairman and ranking member of the Committee on Commerce, Science, and Transportation, said last week in a joint statement.

Some in Congress have even begun to threaten regulation of an industry that has long fought against any curb of its activities.

“These tech platforms who are extraordinarily powerful who’ve been great iconic American success stories - they need to be more forthcoming or Washington is going to start imposing rules and regulations that may not fit,” warned Sen. Mark Warner, D-Virginia, vice chairman of the Intelligence Committee and, himself, a former tech industry entrepreneur and investor.

Warner, who had just months ago insisted on a “light touch” to try to press Silicon Valley into action, has seemed to grow more frustrated with the tech CEO’s since last year, when Facebook, Google, and Twitter sent their top lawyers – instead of coming themselves – to the Intelligence panel to testify regarding their role in Russia’s 2016 interference.

“Facebook has -since the beginning of this investigation - have been reluctant, to say the least, to be fully forthcoming,” Warner said, adding, “I think it’s time for the CEO, Mr. Zuckerberg, and other top officials to come and testify and not tell part of the story but tell the whole story of their involvement, not only with the Trump campaign but their ability to have their platform misused by the Russians.”

Last Thursday, Facebook sent a handful of senior staff to brief aides to a number of key Senate and House committees on the most recent controversy.

The same panels on both sides of Congress who are demanding that Zuckerberg appear also want to hear from Cambridge Analytica executives, including its now-suspended CEO Alexander Nix and former data firm employee Christopher Wylie. The latter told ABC News that he had already accepted House Permanent Select Committee on Intelligence’s invitation.

“One of the reasons why I’m speaking out is because I think that it’s really concerning that no one has really investigated Cambridge Analytica and its role in the 2016 election,” Wylie told ABC News in a recent interview.

Rep. Adam Schiff, D-California, the top Democrat on the Intelligence panel, also invited Russian-American researcher Aleksandr Kogan, who developed the initial app approved by Facebook to collect data on 227,000 of its users.

Kogan previously told ABC News that Facebook and Cambridge Analytica are making him a “scapegoat.”

ABC News also reported Monday that Government watchdog group Common Cause filed a pair of legal complaints with the Federal Election Commission (FEC) and the Department of Justice accusing Cambridge Analytica LTD, its parent company SCL Group Limited, CEO Alexander Nix, SCL co-founder Nigel Oakes, data scientist Alexander Tayler, and former employee-turned-whistleblower Christopher Wylie of violating federal election laws that prohibit foreigners from participating directly or indirectly in the decision-making process of U.S. political campaigns.