The hackers sent out tens of thousands of emails from an FBI email account warning about a possible cyberattack, according to the Spamhaus Project, which tracks spam and related cyber threats. The FBI said it, along with the Cybersecurity and Infrastructure Security Agency, is “aware of the incident this morning involving fake emails from an @ic.fbi.gov email account.”

“This is an ongoing situation and we are not able to provide any additional information at this time,” the FBI said in a statement.

The FBI has multiple email systems, and the one that appears to have been hacked on Saturday is a public-facing one that agents and employees can use to email with the public, according to Austin Berglas, head of professional services at the cybersecurity company BlueVoyant. There’s a separate email system agents are required to use when transmitting classified information, he said.