A Russian propaganda apparatus was successful in spreading fake or false news stories during the recent US election, Washington Post reports. The findings come from a new, unpublished report provided to the Post that found more than 200 websites responsible for publishing Russian propaganda during the election cycle. These sites had a combined readership of 15 million Americans. (Update: The New Yorker observes that there are significant reasons to doubt the conclusions of “PropOrNot,” which led to the original report on an alleged Russian propaganda effort by The Washington Post.)

The campaign reportedly included the use of thousands of botnets, a network of websites and social media accounts, and a team of people paid to push conspiracy theories online. Some of the most common propaganda stories claimed that Hillary Clinton’s health was declining, that people were paid thousands of dollars to protest Trump, and, in the weeks leading up to election day, that the election was rigged.

When these stories were published on Facebook, they were viewed around 213 million times, the Post reports.

As the Post points out, this is not the first report to come to this conclusion. At the start of November, similar findings were published on the security blog War on the Rocks. That report, from Foreign Policy Institute fellow Clint Watts and researchers Andrew Weisburd and J.M. Berger, found “organized hordes of trolls” on Twitter and Facebook who would defend Russian foreign policy to any detractors and attempt to erode trust in mainstream news sources. These trolls would often present themselves on social media as “attractive young women eager to talk politics with Americans.” The researchers concluded that this propaganda effort was an attempt to undermine Americans’ faith in the US government.

Last month, Russia was found to be behind the hack on the Democratic National Committee which lead to the publication of Clinton campaign chair John Podesta’s emails by WikiLeaks.

Update 12/12/16, 9AM ET: Story updated to include a rebuttal from The New Yorker on PropOrNot’s evidence.