Several emergency rooms that shut down after a criminal cyberattack hit their parent company are resuming service, though lingering problems remain for some patients. 

Multiple hospitals across four states shut down emergency services after hackers attacked Ardent Health Services on Thanksgiving Day, locking up their computer networks and demanding a ransom payment.

Several of the hospitals are still diverting some crucial patients but otherwise are resuming normal emergency services, spokespeople for the regional hospital systems said.

Ardent didn’t respond to a request for comment Wednesday. Its last update on its website, posted Monday, said the company “proactively took its network offline, suspending all user access to its information technology applications, including corporate servers, Epic software, internet and clinical programs.”

Epic is a common health care program that stores patient medical information.

Two New Jersey hospitals that had previously refused all emergency patients, the Hackensack Meridian locations in Westwood and Montclair, are now accepting all patients except some stroke victims. Hospitals in the UT Health Network in Texas are no longer diverting patients.

In New Mexico, Lovelace Westside Hospital is still diverting intensive care and critical patients to other hospitals, while Lovelace Regional Hospital has resumed normal service.

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A spokesperson for the Ardent-owned hospital system in Oklahoma, who said Monday that hospitals there weren’t accepting emergency room patients, didn’t respond to a request for comment Wednesday.

The disruption to hospitals did require some patients to reschedule procedures, though nobody is known to have died because of the cyberattack.

Annie Wolf told NBC News that she had scheduled open heart surgery with an Ardent-owned hospital in Tulsa, Oklahoma, on Monday. The hospital called her Saturday to tell her it wouldn’t be able to perform the surgery, as staff members couldn’t access medical records.

“At the moment I don’t have a game plan, because I don’t know when it’s happening,” she said. “It’s sort of like I’m back on the waiting wagon, and that’s not good.”

Her husband, Eric, said he was “furious” that hackers “would specifically target a health care system and put lives in jeopardy.”

“It really upsets me that I’m powerless to do anything about it,” he said.