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Microsoft is currently reviewing its sales records to determine whether trolls aligned with the Russian government purchased ads on Bing or other company products during the 2016 U.S. presidential race.

The decision to conduct an internal investigation comes as Microsoft’s tech industry peers — Facebook, Google and Twitter — contend with parallel probes by the U.S. Congress into the extent to which Kremlin-backed agents spread disinformation on their platforms around Election Day.

Silicon Valley’s Russia ads problem, explained The Recode guide to what Facebook, Google and Twitter have found on their sites, and how the U.S. government is responding.

“We take reports of misuse of our platform seriously,” a Microsoft spokesman said late Monday. “We are therefore investigating and if inappropriate activity is found, we will take steps to minimize such misuse in the future.” Reuters first reported the news.

Some other tech giants — including Oath, formerly Yahoo — have not answered whether they’ve opened their own, similar inquiries in recent weeks, or what they may have found. An Oath spokeswoman did not immediately respond to an email seeking comment Monday.

Facebook said it has so far found that 470 Russian-tied profiles purchased about 3,000 advertisements that sought to stoke racial, religious and other social tensions before and after Election Day.

Those profiles matched with some accounts that sought to sow discord — but did not purchase ads — on Twitter, the company told congressional investigators last month.

Google, for its part, has not announced any findings from its internal review. But sources told Recode on Monday that the tech giant has discovered about $4,700 in search and display ads purchased by agents connected to the Russian government. Google also found tens of thousands of dollars in ads that may have some ties to the country, but might not be state-sponsored, the sources said.

At the moment, only Facebook, Google and Twitter have been invited to testify at two hearings to be held by the House and Senate Intelligence Committees, which are investigating the Kremlin’s suspected election interference. Facebook and Twitter both have confirmed their plans to attend the sessions, scheduled for Nov. 1, while Google has declined to comment.

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