Hackers outside of the United States successfully penetrated some of the US’ election systems, the FBI has revealed. At least two state election databases were recently hacked and those hacks came after other election-related attacks that may have been carried out by Russia.

The FBI says election officials should be focused on increasing security. Jeh Johnson, secretary of Homeland Security, previously said his department would help states increase security around their voting systems due to concerns about foreign hackers in this election cycle.

Arizona and Illinois appear to be the states that were targeted. In Illinois, the hack resulted in data on 200,000 voters being stolen. Data wasn’t taken in the Arizona case.

Based on its investigation, the FBI believes those attacks were related and likely came from the same group.