The U.S. government issued a private warning Russia there would be “severe consequences” if it interferes with Tuesday’s elections.

The warning came after concerns that election systems in Illinois and Arizona were hacked, according to ABC News.

They also come in light of emails released by WikiLeaks from both the Democratic organizations and from Hillary Clinton campaign chairman John Podesta.

In October, the Director of National Intelligence James Clapper claimed Russia’s “senior-most officials” allowed the cyberattacks to tamper with the U.S. electoral system.

Much of the intelligence community says large-scale disruption of the election system is nearly impossible.

“The [U.S. Intelligence Community] and the Department of Homeland Security (DHS) assess that it would be extremely difficult for someone, including a nation-state actor, to alter actual ballot counts or election results by cyber attack or intrusion,” the Department of Homeland Security and the Office of the Director of National Intelligence said in a statement.

But U.S. officials told ABC News they are concerned with an attack that would be big enough to undermine confidence in the system or to cause confusion over results.