Officials have investigated at least 12 cases of hepatitis linked to a heart clinic in West Virginia.

The viruses have been linked to injectable medications given during cardiac stress tests at the Raleigh Heart Clinic, local news media outlets reported.

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Eight patients receiving cardiac stress tests have tested positive for hepatitis C and four others have tested positive for hepatitis B, said Allison Adler, director of communications for the Department of Health and Human Resources. Adler said there has been no evidence of HIV transmission.

The investigation started in November 2014, after a patient with no risk factors for hepatitis C was diagnosed with the virus.

State Health Commissioner Dr. Rahul Gupta said Thursday that during inspections, Department of Health and Human Resources investigators witnessed several areas of improvement for the clinic.

"There are single-use vials," he said of the clinic. "You have a drug in one vial for a patient's one-time use. But we find that it is often used for multiple uses. So that's one way of transmitting it because you can change the needle but there's always a risk with the vial."

Gupta said the extent of how many individuals were exposed to the pathogens is unknown.

Officials are now urging about 2,300 patients of the Raleigh Heart Clinic to be tested for hepatitis B and C as well as HIV.

A class-action lawsuit has been filed by patient Pamela Vines against the clinic on behalf of patients who had cardiac stress tests.

The Charleston Gazette-Mail reports that the Raleigh Heart Clinic has not commented on the matter.