The top Democrat on the House Intelligence Committee, Representative Adam B. Schiff of California, said on Monday that it should not be surprising that Russians were using Google as well as Facebook and Twitter. The only thing that is surprising, he said, is that it took so long for Google to find the activity.

“It will take more time and length and breadth to know what Russia did on social media,” Mr. Schiff said. “But the themes are consistent across platforms: the desire to help Donald Trump, to hurt Hillary Clinton and the desire to set Americans against each other.”

In addition to the Senate committee hearing, Google and Facebook are expected to testify at another Nov. 1 hearing before the House Intelligence Committee. Twitter was also invited to the House committee hearing, but it was not clear on Monday whether officials from the company planned to attend.

Facebook has said the Russian company had placed 3,000 ads on its network at a cost of about $100,000. Last month, Twitter said it had found about 200 accounts that appeared to be linked to a Russian campaign to influence the election.

Google is the only company that sells more digital advertising than Facebook, and its role in the coordinated Russian campaign has been a source of intense speculation in Washington and Silicon Valley. The Washington Post reported that Google had found that Russian agents hoping to spread misinformation had spent tens of thousands of dollars on the company’s advertising platforms.

But Google’s investigation has not found the same type of pinpoint advertising that Russian agents conducted on Facebook. The social network allows advertisers to target its audience with more specificity than Google, including users with a wide range of political leanings.

The 2016 presidential election was the first time that Google allowed targeting by political leanings and it allowed just two categories — left-leaning and right-leaning.