Dozens of patients of an Oklahoma dental clinic shuttered for unsanitary conditions have tested positive for hepatitis, Tulsa health officials said Thursday. The clinic of oral surgeon W. Scott Harrington was shut down in March after an investigation.

So far 57 current and former patients who may have been treated with dirty equipment have tested positive for hepatitis C and three tested positive for hepatitis B, the Tulsa Health Department said in a statement.

“We understand these first reported test results may be of concern,” said THD Director Dr. Bruce Dart. “Thorough investigations are routinely conducted upon notification of a positive report for these infections. This response will be handled in the same manner, as disease investigation is a core public health service and staff are well trained to conduct this type of response.”

Positive results for HIV have also been reported, but Oklahoma law prohibits public reporting of cases fewer than three.

On March 28, investigators from the Oklahoma State Department of Health and Tulsa Health Department urged as many as 7,000 patients of the Tulsa dental clinic to be screened for hepatitis B, hepatitis C and HIV, after a patient of Harrington's had tested positive for hepatitis C. The patient had no other risk factors for the infectious disease. Inspectors for the Oklahoma Dentistry Board called Harrington "a menace to the public health" after finding dirty instruments and improper sterilization procedures, the Associated Press reported.

Current and former patients who tested positive are being personally contacted and counseled, state health officials said. Patients with negative results will receive letters in the mail.

It's possible at least some of the positive infections are not related to exposure to procedures at the dental practice, health officials said.

“This is a complex investigation,” State Epidemiologist Dr. Kristy Bradley said in a statement. “The next phase will include more in-depth interviews of persons who test positive to determine the likelihood that their exposure is associated with their dental surgical procedure at the Harrington practice. We will certainly continue to keep the public informed as we learn more.”

According to the statement, an estimated 4,944 persons are living with HIV/AIDS in Oklahoma and as many as 68,000 Oklahomans may be infected with hepatitis C.

So far, the state lab has screened 3,235 current and former patients for the bloodborne viruses. It's unknown how many patients have been tested through private doctors.

Harrington voluntarily gave up his license and is reportedly cooperating with the investigation.

NBC's KJRH contributed to this report. For more visit KJRH