The State Department has completed its investigation into the use of a private email by Ex Secretary of State Hillary Clinton and has found violations by 38 people, some of whom could face disciplinary sanctions.

The investigation initiated more than three years ago determined that the 38 people were “guilty” in 91 cases of sending confidential information that went to Clinton’s personal mail, according to a letter sent to Republican Senator Chuck Grassley and released Friday. The 38 cited are retired or active employees of the State Department.

According to the report, the investigators “found no persuasive evidence of systematic and deliberate mismanagement of confidential information.” However, he clarified that the use of private mail by Clinton increased the vulnerability of confidential information.

The investigation covered 33,000 email messages that Clinton delivered when the use of her private email account took public status. The department said it found 588 violations regarding information considered then or now confidential, but could not assign blame in 497 cases.

For retired or active officials, guilt means that violations will be registered in their service records to take into account when requesting or renewing their security credentials. Acting officials could suffer penalties, but it was not immediately clear what they would consist of.