Facebook reported in its blog post Wednesday that about one-quarter of the ads in question were “geographically targeted,” although company officials declined to provide specifics about what areas or demographic groups were the recipients. Of those targeted ads, the company said, more ran in 2015 than 2016.

Rep. Adam B. Schiff (Calif.), the senior Democrat on the House Intelligence Committee, said Wednesday that the disclosure by Facebook confirmed one of the ways Russia sought to interfere in U.S. politics and serves as a “profound warning to us and others about future elections.”

“This is a very significant set of data points produced by Facebook,” Schiff said, adding: “Left unanswered in what we received from Facebook — because it is beyond the scope of what they are able to determine — is whether there was any coordination between these social media trolls and the campaign. We have to get to the bottom of that.”