NEW YORK (AP) — The FBI is warning state officials to boost their election security in light of evidence that hackers breached related data systems in two states.

In a confidential “flash” alert from its cyber division, first reported by Yahoo News and posted online by others, the FBI says it’s investigating the pair of incidents and advising states to scan their systems for specific signs of hacking.

The FBI isn’t naming the states it says were breached.

The Aug. 18 warning came just days after Homeland Security Secretary Jeh Johnson hosted a call with secretaries of state and other state election officials to talk about cybersecurity and the election infrastructure.