Sinclair Broadcast Group was targeted by a ransomware attack that caused disruption in the broadcast operations this weekend at several television stations.

According to the company’s regulatory filing, Sinclair began the investigation on Saturday. The investigation revealed that several of its servers and workstations were encrypted with ransomware. The hackers also took some data from the server.

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The cyberattack “has caused, and may continue to cause, disruption to parts of the Company’s business, including certain aspects of its provision of local advertisements,” the filing with the SEC said, according to a report by the Washington Post.

The company is “working diligently to address the incident and to restore operations quickly and securely,” Leigh Anne Arnold, a Sinclair spokesperson was quoted as saying by the Washington Post.

The severity of the disruption has not been revealed by the company but disruption was reported in several channels owned by it on Sunday.

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“Technical issues have kicked us off the air this morning,” tweeted Phil Kelly, a Columbus, Ohio, television host with the ABC6/Fox28 station. 

“It’s a corporate wide problem that our engineers are working hard to fix. Hopefully see you soon?” the tweet added

The attack disrupted several stations owned by the Sinclair Group due to many sections of their systems being connected through the same “Active Directory domain”. The connection made it hard to isolate the breach. But the attack did not appear to have reached a Sinclair system called “the master control,” allowing Sinclair to replace local feeds with a national one, the Recorder reported citing a company source.

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Sinclair is the latest to face ransomware attacks in the United States. Colonial Pipeline’s faced a similar attack on their business systems, which disrupted fuel operations to much of the East Coast in May. A JBS meat processing plant was targeted a few weeks later.