But he didn’t narrow down the potential culprits to just other countries.

American intelligence agencies are concerned about reports that foreign governments may be attempting to undermine the November 8 U.S. elections through cyber attacks, Admiral Mike Rogers, the director of the National Security Agency, said on Tuesday.

“We continue to be actively concerned,” Rogers told a Senate hearing, responding to a question from Senator John McCain, chairman of the Senate Armed Services Committee.

Marcel Lettre, Under Secretary of Defense for Intelligence, testified that the government is taking any such activities “quite seriously” and said an “aggressive investigation” is under way.