One of the largest gambling companies in the U.S. said a cyberattack last week caused massive disruptions to their operations, forcing them to take some systems offline.

International Game Technology (IGT) notified the U.S. Securities and Exchange Commission on Tuesday that it became aware of the cyberattack when it “experienced disruptions in portions of its internal information technology systems and applications” on Sunday.

“The Company has also proactively taken certain systems offline to help protect them. The Company's ongoing investigation and response include efforts to bring its systems back online,” the company said. 

The company added that it had not yet determined if it would impact its bottom line, and had implemented some operational workarounds to continue servicing its customers.

IGT provides systems and technology for lotteries, gambling machines and sports betting. The company has more than 11,000 employees around the world and reported a revenue of $1.9 billion for the first nine months of the year. 

No hacking group has taken credit for the attack as of Thursday but ransomware operations have repeatedly targeted casinos and lotteries over the last year. 

Ohio’s state lottery was impacted by a ransomware incident last year and the disruption of MGM Casino last fall caused more than $100 million in damages. Yesterday, the Justice Department unsealed charges against several of the hackers involved in the incident.