Knoxville, TN has suffered a major ransomware attack, forcing it to shut down its entire network.

According to BleepingComputer, a notice was sent out to city employees Thursday morning informing them of the issues.

“Please be advised that our network has been attacked with ransomware,” reads the notice.

“Information Systems is currently following recommended protocols. This includes shutting down servers, our internet connections, and PCs. Please do not log in to the network or use computer applications at this time.”

So far, Knox County government computers were not impacted. Police and fire department operations are intact, although neither can access the network.

As BleepingComputer points out, no group has yet claimed responsibility, although the FBI is investigating the incident. At the same time, officials said no personal data or credit card information was accessed or stolen.

Ransomware has become one of the biggest threats to online security, with attacks costing the US an estimated $7.5 billion in 2019. Knoxville is just the latest example of the problems these attacks can cause.