Great Plains Regional Medical Center has confirmed a ransomware attack that compromised the personal information of over 133,000 patients.

In a statement, the hospital said it discovered the attack on September 8; however, investigators determined that hackers accessed its systems three days earlier. During this time, files were encrypted, and sensitive data was copied.

The compromised information includes names, Social Security numbers, driver’s license numbers, health insurance details, and medical information such as diagnoses and medications.

The hospital also stated that it has restored its systems and returned to normal operations but acknowledged that some patient data could not be recovered. Letters have been sent to affected individuals, and the hospital is offering free credit monitoring to those whose Social Security or driver’s license numbers were involved.

So far, no ransomware group has claimed responsibility for the attack.