Facebook, Google and Twitter plan to tell congressional investigators this week that the scope of Russia’s campaign to spread disinformation on their sites — and to potentially disrupt the 2016 U.S. presidential race — is much broader than the companies initially reported. At Facebook, roughly 126 million users in the United States may have seen posts, stories or other content created by Russian government-backed trolls around Election Day, according to a source familiar with the company’s forthcoming testimony to Congress. Previously, Facebook had only shared information on ads purchased by Kremlin-tied accounts, revealing that they reached more than 10 million U.S. users.

Google, which previously had not commented on its internal investigation, will break its silence: In a forthcoming blog post, the search giant confirmed that it discovered about $4,700 worth of search-and-display ads with dubious Russian ties. It also reported 18 YouTube channels associated with the Kremlin’s disinformation efforts, as well as a number of Gmail addresses that “were used to open accounts on other platforms.” And Twitter will tell Congress that it found more than 2,700 accounts tied to a known Russian-sponsored organization called the Internet Research Agency, according to sources familiar with its testimony. Twitter initially informed lawmakers about just 200 known accounts. The company will also release a new study that shows the extent to which Russian-based automated accounts, or bots, of all sorts tweet on its platform. 20161217_blp902

In sharing these findings with congressional investigators, the three tech giants plan to emphasize that Russian-fostered disinformation — while troubling — amounted to only a small portion of the ads and other content published regularly on their platforms. Facebook, for example, hopes to highlight that its U.S. users are served more than 200 stories in their News Feeds each day, according to a source familiar with its thinking. Still, the companies’ explanations may not satisfy an ever-expanding chorus of critics on Capitol Hill. Lawmakers are increasingly demanding that Facebook, Google and Twitter step up their efforts to counter the Kremlin’s attempts to sow political and social discord — or else face more regulation by the U.S. government.