The ads appeared mainly alongside Google’s search results or on websites that use Google ads outside the search company’s own sites. It was not clear whether such ads appeared on YouTube or the Gmail email service, the person said.
There is a chance that Google may find other ads from Russian-linked accounts, the person familiar with the investigation said.
Microsoft, a distant rival to Google in the internet search and advertising market, said Monday evening that it too was examining whether suspected Russian agents used its services to show political ads during the 2016 election. Microsoft’s Bing search engine accounts for about 23 percent of searches in the United States, compared with more than 63 percent for Google, according comScore, an internet measurement firm.
Google has been called to testify at a Senate Intelligence Committee hearing on Nov. 1. But it has so far escaped the intense scrutiny confronting Facebook after the social network admitted that it discovered 470 profiles and pages to the internet Research Agency, a Russian company with ties to the Kremlin.
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.
However, Google has not found any evidence that the ads from the accounts suspected of having ties to the Russian government used these political categories or geographic parameters to focus on specific groups, the person familiar with the company’s investigation said. The ads were much more broad, aimed at English-language queries or any users in the United States, for example.
A Google spokeswoman, Andrea Faville, said the company had a policy that limited political ad targeting and prohibited targeting based on race and religion.
“We are taking a deeper look to investigate attempts to abuse our systems, working with researchers and other companies, and will provide assistance to ongoing inquiries,” Ms. Faville said.
On Facebook, fake Russia-linked accounts — in which fictional people posed as American activists — promoted inflammatory messages on divisive issues. Those accounts bought advertising to promote those messages and reach a bigger audience within the Facebook universe, while promoting the incendiary posts to different locations or people with established political leanings for maximum impact.
The Russian-linked accounts did not target ads based on political affiliation, but it raises the question of why Google allowed such targeting for the 2016 election when it had not done so in the past. The only location where Google allows ad targeting by political affiliation is the United States.
Google is working with Jigsaw, a think tank owned by its parent company, Alphabet. Jigsaw has been doing research for 18 months on fake news and misinformation campaigns and Google is applying some of those findings in the investigation into Russian election meddling, the person said. It is also working with other technology companies like Facebook and Twitter, in addition to independent researchers and law enforcement.