Employees of Melbourne Heart Group in Malvern, Australia, have been unable to access patients’ medical records following a January ransomware attack that encrypted the health care provider’s files.

The cardiology clinic disclosed the incident today on its website’s home page. “We have been assured that no patient’s privacy has been compromised in any way,” the statement reads. “We are working through this issue with our IT provider and hope to resolve it as soon as possible.”

Melbourne Heart Group claims patient privacy was not affected, and has assured the public that its clinics are “operating as usual” and patients are not being turned away.

Approximately 15,000 patient files have been encrypted, according to a report in The Age, which notes that the ransomware is believed to be from North Korea or Russia, although the origins of the criminals are unknown.