Sen. Mark Warner

(ABC News) Congressional investigators say they are increasingly concerned about threats to the coming midterm election with multiple probes into Russian meddling in the 2016 presidential election still incomplete with no immediate end in sight. Among their top concerns, according to sources: Russia’s ability to further exploit and potentially influence American voters using social media platforms like Facebook and Twitter to circulate fake political ads containing disinformation.

“I think to believe that Russia’s not attempting in the United States to do things potentially for the ’18 cycle, I think, would be ignorant on our part,” chairman of the Senate Intelligence Committee Sen. Richard Burr R-N.C., said at the Council on Foreign Relations earlier this month. “I think all of my colleagues probably are worried or should be worried about it. I think every state should be worried about it,” he said. Democratic Sen. Mark Warner of Virginia, and Burr’s counterpart on the committee, called the Russia probe “the most important thing I will ever work on.”