April 18, 2013 -- At least 60 people have tested positive for hepatitis or HIV after visiting an Oklahoma dentist slammed by the state dental board for poor sterilization practices, the Tulsa Health Department said today.

Dr. W. Scott Harrington allegedly re-used needles, a practice that can contaminate ostensibly sterile drugs with dangerous diseases. He is also accused of using rusty equipment that was not properly cleaned.

More than 7,000 patients from Harrington's Tulsa and Owasso clinics were sent letters in late March outlining the risk of infection and steps to obtain free blood testing. Of 3,122 patients tested by county health departments so far, 57 tested positive for hepatitis C, three tested positive for hepatitis B, and at least one tested positive for HIV.

"We understand these first reported test results may be of concern," Tulsa Health Department Director Dr. Bruce Dart said in a statement.

The Tulsa and Oklahoma health departments are in the process of notifying patients of the results. Patients who tested positive will be personally contacted, counseled about the disease and directed to resources for care, the agencies said in a statement. Testing may also be recommended for their spouses or partners.

"This is a complex investigation," state epidemiologist Dr. Kristy Bradley said in a statement, stressing that the source of the infections is still under investigation. "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."

A surprise inspection of Harrington's practice March 18, prompted by a patient's positive test for HIV and hepatitis C, revealed the use of old needles and rusty instruments, as well the practice of pouring bleach on patients' wounds until they "turned white," according to a complaint filed by the Oklahoma Board of Dentistry.

"The basic things that everyone knows -- follow CDC guidelines, use clean syringes, don't reuse multi-dose vials in multiple patients, don't use rusted equipment -- those are things even non-physicians know," board president Susan Rogers told ABC News at the time. "Those are basic things. That part makes it egregious."

Instruments used for patients who were known to carry an infectious disease were given an extra dip in bleach on top of normal cleaning methods, according to the complaint. But the tools had red-brown rust spots, indicating that they were "porous and cannot be properly sterilized."

Harrington, who has been practicing for more than 30 years, voluntarily surrendered his state dental license and could face criminal charges. A license revocation hearing before the state dentistry board is set for August 16.

The Tulsa Health Department has set up a hotline at (918) 595-4500 for people with questions.