Milwaukee ? More than 22,000 veterans who underwent prostate biopsies at veterans’ hospitals across the country are being warned that improperly sterilized equipment may have exposed them to deadly viruses.

Officials said Friday it was unlikely someone could get infected by the equipment, and no patient is known to have been sickened.

Still, the U.S. Department of Veterans Affairs decided to offer free blood tests as a precaution after officials in Maine questioned whether the cleaning procedure was thorough enough, said VA spokesman Jim Benson.

The prostate biopsy equipment includes a probe that, if improperly cleaned, could retain traces of body fluids containing the viruses that cause hepatitis or AIDS.