JACKSON, Miss. (AP) — A ransomware attack forced the University of Mississippi Medical Center to close all of its roughly three dozen clinics around the state and cancel elective procedures for a second day on Friday, hobbling one of the state’s largest health care providers.

University officials warned that the shutdown could continue for days as they try to evaluate the extent of the attack, including whether patients’ sensitive information was compromised, and restore network systems they took down as a precaution.

Richard Bell, 55, drove three hours from his home in Oxford the medical center’s main campus in Jackson on Friday only to learn that he wouldn’t be able to get his bloodwork or chemotherapy treatment.

“It was all shut down,” Bell said. “It gets pretty frustrating.”

Bell, who has a form of lymphoma, wasn’t immediately able to reschedule the appointment. University officials said in a statement on Friday they were reaching out to patients who require time-sensitive treatments such as chemotherapy.

Hospitals and emergency rooms remained open, and patients there were receiving proper care, the university said in the statement. Officials were still trying to figure out the extent of the infiltration, but Vice Chancellor LouAnn Woodward said at a news conference Thursday the attack affected “many systems,” including the electronic health record platform.