The city of Vicksburg, Mississippi, shut down its computer systems after detecting a ransomware attack on October 1. Mayor Willis Thompson told the Vicksburg Post the city disconnected its internet operations “just for protection” while investigators determine the scope.

Emergency services were not affected. The city said 911 dispatch, police, fire and utility services continued to operate normally. The main disruption is to in-person utility bill payments, which may be delayed. Officials said no accounts will be shut off and no late penalties will apply while systems are offline.

The city’s water and gas office serves more than 10,000 utility accounts. Vicksburg has brought in outside cybersecurity specialists and is working with the FBI, the Department of Homeland Security and Mississippi state officials.

Investigators have not identified the group behind the attack or said how the attackers got in. The city has not reached a final decision on whether personal or confidential information was accessed, and said it will notify affected people if a data breach is confirmed.