DENVER (CBS4) – There are now six former patients of a dentist accused of reusing needles who have tested positive for either hepatitis or HIV.

It’s not known whether they contracted the diseases from Dr. Stephen Stein’s office. Stein has since surrendered his license as an oral surgeon.

About 8,000 of Stein’s patients were sent letters asking them to get tested. The health department says it’s impossible to definitively tell if the infected patients got sick from Stein.

Stein had offices in Cherry Creek and Highlands Ranch.

The Denver Police Department is also investigating Stein for prescription drug fraud.