The most populous county in Georgia is dealing with an IT outage caused by a cyberattack discovered over the weekend.

Fulton County Board of Commissioners Chairman Robb Pitts held a press conference Monday explaining that the attack affected county office phone systems and online transactions, including those involving firearm and marriage licenses.

“Over the weekend, the Fulton County government learned of a widespread system outage. At this time, we can confirm that the incident was a result of a cybersecurity incident,” Pitts said, adding that it is “under active investigation” by law enforcement..

“That investigation is still in the early stages. So we'll be providing limited information at this time. However, we do want our citizens to be aware that a number of our primary technology platforms are affected by this incident. Three notable examples include our phone system, our court system, and our tax system. We do not yet have a specific timeframe for when these systems will be restored.”

Fulton County has more than 1 million residents and is home to Atlanta. The FBI told local news outlets that it is involved in the investigation of the attack.

The county website has a notice urging residents to email Fulton County Customer Service if they have any questions while their phone systems are down.

Most Fulton County offices are open but the Fulton County Tax Commissioner in downtown Atlanta was closed on Monday. Many other offices will be limited as the IT department works to resolve the outages.

Public computers at county libraries were out of service on Monday but appear to be back as of Tuesday.

Local news stations said residents ran into widespread issues when they showed up to dispute property taxes or go to the DMV.

No group has taken credit for the attack, but last year Georgia’s Forsyth County faced off against the AlphV ransomware gang. The government of Augusta, Georgia also dealt with a ransomware attack in June that disrupted city systems.

Several other institutions — including the Georgia State Bar and Savannah College of Art and Design — have dealt with cyberattacks in the last two years.