The U.S. Department of Health and Human Services says the personal information of more than 500 people may have been compromised.
The hospital's system was hacked sometime between Jan. 17 and Feb. 1.
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Loretto says it is reviewing its files and will notify those who may have been affected and determine what was accessed.
Anyone with questions on the incident should contact cyber.incident@lorettohospital.org or write to Loretto at 645 S. Central Ave., Chicago, Illinois, 60644, Attn: Information Systems CIO.
This is a developing story; check back with ABC7 Chicago for updates.