(Bloomberg) -- Sinclair Broadcast Group Inc. said it has launched an investigation after finding its servers and workstations were encrypted with ransomware.

In a statement, Sinclair, which owns dozens of local TV and sports channels in the U.S., said it found on Sunday that “certain office and operational networks were disrupted” and data was taken from its computer network. The incident also affected advertisers on its local TV stations. 

The company said it “cannot determine at this time whether or not such event will have a material impact on its business.” Sinclair has notified law enforcement and a cybersecurity firm is looking into the incident.

Ransomware is a type of cyberattack in which hackers encrypt computer files then demand payment to unlock them. Hackers are increasingly setting their sights on local TV station owners. In June, Cox Media Group, a local-TV broadcaster owned by Apollo Global Management, was reportedly hit by a cyberattack.

Sinclair shares were down 2.1% at 10:03 a.m. in New York. They are down about 16% this year compared with a 19% increase in the S&P 500.

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