A nurse at Glendale (Calif.) Adventist Medical Center was fired Nov. 30 after accessing more than 500 patient records without authorization, according to the Los Angeles Times.
Glendale Adventist officials discovered the breach during a security review in June. Officials later uncovered that the source of the breach was an employee and not an external hack.
The nurse accessed 528 patients' information without authorization, including 88 records from Glendale Adventist's sister hospital White Memorial Medical Center based in Boyle Heights, Calif.
Glendale Adventist officials did not disclose what type of information was accessed, but officials said it's possible the data included patient demographics, names, dates of birth, addresses, diagnoses and Social Security numbers.
Medical center officials have reportedly notified all affected patients of the breach.
"We take this breach very seriously, and as a result we are taking additional steps to both ensure this event is resolved as well as ensuring these events don't happen in the future," a hospital statement reads.