(NewsNation) — The data of nearly 2.2 million patients was potentially exposed in a ransomware attack on Michigan-based McLaren Health Care, the company confirmed.

McLaren made the notification in a data breach filing with the Maine Attorney General’s Office, revealing that hackers were in its system for three weeks from July 28 to Aug. 23 earlier this year.

Hackers were able to access names, Social Security numbers, health history and billing information, among other records, of 2,192,515 patients. The company notified Maine because it said 77 residents in the state were impacted.

McLaren said in its data breach filing with Maine that it “moved quickly to investigate and respond to the incident,” notified law enforcement and is implementing additional safeguards to its systems.

News of the cyberattack first broke in October when cybercriminal gang ALPHV (or BlackCat) claimed responsibility, according to the Michigan Attorney General’s Office. At the time of the notification given by the attorney general, the number of exposed patients was unknown.

The group is also believed to be responsible for ransomware attacks on MGM Resorts that shut down casino operations for over a week.

McLaren is facing multiple class-action lawsuits in relation to the data breach.