The Missouri Department of Health and Senior Services (DHSS) has determined that a doctor’s credentials were stolen and used to fraudulently certify patients for medical cannabis, according to a KMAland.com report.

The DHSS launched an investigation last month after roughly 600 patients submitted physician certification forms with unauthorized signatures.

The credentials of a doctor who is registered with the state to certify patients for medical cannabis were being used without that doctor’s knowledge to certify the affected patients, primarily through telemedicine visits, KMAland.com reported.

A department spokesperson told the news outlet that an involved party informed the state of the fraudulent certifications, and the DHSS has worked to find additional patients who might be affected.

The state is notifying all affected patients and issuing a deadline for them to submit a valid medical cannabis certification, KMAland.com reported. If they are unable to submit a valid certification by the deadline, they will lose their medical cannabis cards.

The case has been turned over to the Missouri Attorney General’s Office and the Board of Healing Arts, according to KMAland.com.