The assault started on April 18, when some of the systems in the city’s internal network were reported as unresponsive, and prompted the immediate activation of the incident response plan.

To secure its network, Abilene disconnected critical assets and the systems that were impacted by the attack, the city’s officials announced on Monday.

“We also launched an investigation and engaged industry-leading cybersecurity experts to determine the nature and scope of the incident and notified relevant authorities,” the officials said.

The city’s IT department has been working over the weekend to restore services and minimize impact on operations, Abilene’s officials said, noting that systems are monitored for any unusual activity.