Hackers have infected 23 organisations connected to local government in the US state of Texas with ransomware.
Officials indicated the attack over the weekend was co-ordinated.
The Texas Department of Information said the attack had primarily affected smaller local government departments.
A spokesman said the situation was still ongoing on Monday morning.
Texan authorities have drafted in cyber-security experts, as well as the military and counter-terrorism units, to help bring systems back online.
In a statement, the Texas Department of Information Resources said evidence suggested the attacks “came from one single threat actor”.
Officials did not release specific details of the affected departments or say whether the cyber-criminals had specified a ransom amount.