The FBI’s Cyber Division has issued a warning that foreign hackers are targeting — and perhaps even penetrating — state election and voter registration systems in the US.

The alert comes in the wake of a Russian hacker gaining login access to Arizona election systems, the Wall Street Journal reported.

“[D]ue to what the FBI characterized as a credible threat to our voter registration system,” some election systems were taken offline, a spokesman for the Arizona secretary of state told the Journal.

“We got word from the FBI that a credential was leaked by a Russian hacker. … The hacker apparently was a known entity to law enforcement.”

A cyberattack has also been targeted at Illinois election systems — specifically, the state’s voter database.

The headline of the FBI alert reads: “Targeting Activity Against State Board of Election Systems.”

The FBI flash warns of a threat coming from specific IP addresses: “The FBI received information of an additional IP address, 5.149.249.172, which was detected in the July 2016 compromise of a state’s Board of Election Web site. Additionally, in August 2016 attempted intrusion activities into another state’s Board of Election system identified the IP address, 185.104.9.39 used in the aforementioned compromise.”

And the alert calls on other states to notify the FBI if further attacks are suspected.

“The FBI is requesting that states contact their Board of Elections and determine if any similar activity to their logs, both inbound and outbound, has been detected. Attempts should not be made to touch or ping the IP addresses directly,” reads the warning.