Dallas was hit with a computer ransomware attack Wednesday that brought down its Police Department and City Hall websites and caused some jury trials to be canceled, officials said.

The outage didn't appear to affect 911 calls. However, it did cause problems with a computer-assisted dispatch system that is used to help firefighters respond to emergency calls, Dallas Fire-Rescue spokesman Jason Evans told the Dallas Morning News.

"DFR has been running on manual dispatch operations since early this morning," Evans said.

RUSSIAN RANSOMWARE ATTACK SOFTWARE TARGETS APPLE MAC AND MACBOOK

Ransomware involves hackers essentially holding a target computer or computer system hostage by encrypting its files and demanding payment, often via bitcoin. Ransomware can target individuals, businesses, and governments alike.

In a statement, the city said the attack had only a limited impact on delivery of city services.

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"The City team, along with its vendors, are actively working to isolate the ransomware to prevent its spread, to remove the ransomware from infected servers, and to restore any services currently impacted," read the statement.

The city didn't indicate whether any financial demands had actually been made or provide other details of the incident.

The Police Department and City Hall websites were down Wednesday afternoon, officials said, and the Municipal Court posted a notice on its website that all jury trials and duties were canceled for the day.