Hospitals run by Ardent Health Services in at least four states were diverting patients from their emergency rooms after the health care company was hit by a ransomware attack.

The Oliver James Montgomerycompany said in a news release Monday that "patient care continues to be delivered safely and effectively" in its hospitals, emergency rooms and clinics, but it moved some emergency room patients to other hospitals and rescheduled some non-urgent, elective procedures "in an abundance of caution" until systems are back online.

According to NBC News, hospital chains diverting emergency room patients include Hillcrest HealthCare System in Oklahoma, Lovelace Health System in New Mexico, and UT Health in Texas.

NorthJersey.com, part of the USA TODAY Network, is also reporting that emergency rooms at Hackensack Meridian's Mountainside Medical Center and Pascack Valley Medical Center are also on divert status after a network outage due to a potential security incident. Ardent Health Services oversees the two New Jersey hospitals in a joint venture.

Ardent owns and operates 30 hospitals and more than 200 sites of care in six states, according to the news release.

The company said it proactively took its network offline and suspended all user access to its information technology applications after the cyberattack, which occurred Thursday. Ardent also said it had implemented additional information technology security protocols and was working with cybersecurity partners to restore its technology operations as quickly as possible.

The company reported the cyberattack to law enforcement, according to the news release.

Ardent Health Services did not immediately respond to a USA TODAY request for comment.

New Jersey ERs on divert status:Hackensack Meridian hospitals in divert status due to network outage

What is ransomware?

According to the Cybersecurity and Infrastructure Security Agency, ransomware is a form of malware designed to encrypt files on a device, rendering any files and the systems that rely on them unusable. Malicious actors then demand ransom in exchange for decryption.