Russian operatives spent tens of thousands of dollars on ads on YouTube, Gmail and Google search, an internal Google investigation has uncovered.

The ads are the first evidence Google has found that show Russia was trying to use the company’s advertising platform to influence the 2016 US presidential election, according to a Washington Post report on Monday.

The ads do not appear to have originated from the same Kremlin-backed source that bought ads across Facebook, said sources familiar with the investigation, suggesting that a number of entities could share responsibility in the Russian effort to spread disinformation.

Google has for the most part avoided the level of scrutiny aimed at fellow Silicon Valley stalwart Facebook, which handed over 3,000 Russia-backed ads to Congress earlier this month. But Google’s own investigation got its spark from pressure by  Congress to determine the extent to which Russian operatives used social media and bought ads across internet platforms.

Facebook’s role extends beyond ads to the sorts of hoax stories that showed up in people’s news feeds. Over the weekend, the its security chief defended the social media giant’s use of algorithms, describing the problem of fake news as larger and more complicated than many realize.

“I am seeing a ton of coverage of our recent issues driven by stereotypes of our employees and attacks against fantasy, strawman tech [companies],” Facebook’s Alex Stamos said in a Twitter thread. “Nobody of substance at the big companies thinks of algorithms as neutral.”

On Nov. 1, Google officials are expected to testify in front of Congress on the issue, along with representatives from Facebook and Twitter.

Google did not immediately respond to request for comment.

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