A hack that caused a small Texas town’s water system to overflow in January has been linked to a shadowy Russian hacktivist group, the latest case of a U.S. public utility becoming a target of foreign cyberattacks.

The attack was one of three on small towns in the rural Texas Panhandle. Local officials said the public was not put in any danger and the attempts were reported to federal authorities.

“There were 37,000 attempts in four days to log into our firewall,” said Mike Cypert, city manager of Hale Center, which is home to about 2,000 residents. The attempted hack failed as the city “unplugged” the system and operated it manually, he added.

In Muleshoe, about 60 miles to the west and with a population of about 5,000, hackers caused the water system to overflow before it was shut down and taken over manually by officials, city manager Ramon Sanchez told CNN. He did not immediately respond to phone calls from The Associated Press seeking comment.