There has been a data breach at Natural Health Services, including its location in Windsor.

It involves the personal health information of about 34,000 medical marijuana patients that was accessed in a data breach of an electronic medical record system used by NHS and its parent company Sunniva Inc.

NHS says patients have been informed in the last week of the breach that occurred between Dec. 4, 2018 and Jan. 7.

It says the breach didn't involve any financial, credit card or social insurance number information since those aren't collected from patients.

However, personal injury firm Diamond and Diamond -- which has announced a proposed class-action lawsuit against NHS and Sunniva -- says it did involve diagnostic results, health-care numbers and personal contact information.

"What is more integral than the preservation of our health information?" said Jeremy Diamond, Manager Partner at Diamond and Diamond Lawyers. "All individuals that filled out these online forms could be affected by this egregious breach."

The law firm also confirms to CTV News that the first complainant was from the Windsor area.

The company, which operates seven clinics in Canada including in Windsor, says it has been working with privacy protection and law enforcement authorities to investigate and respond to the breach.

A dedicated hotline has been set up to field patient inquiries, at 1-888-297-0573.

"We value our patients and understand the importance of protecting personal information and apologize to the patients whose personal information has been improperly accessed and for any frustration or inconvenience that this may cause," stated NHS president Dr. Mark Kimmins. “We are taking this situation very seriously and are taking the necessary steps to prevent a situation like this from happening again.”

With files from The Canadian Press