RENO, Nev. (AP) — A hepatitis C outbreak affecting more than 80 people and exposing tens of thousands more was caused by workers reusing syringes at a Las Vegas clinic, federal health officials said Friday.

The Centers for Disease Control and Prevention report bolsters earlier conclusions by state and county officials, which led to the biggest public health notification operation in U.S. history.

State health officials contacted the CDC on Jan. 2 after two people treated at the now-closed Endoscopy Center of Southern Nevada were diagnosed with acute hepatitis C.

The practice of reusing syringes with the sedative propofol "was observed, and interviews suggested it was a common practice," the CDC investigators said in a report to the Nevada State Health Division.

"This was considered the most likely mode of transmission," the report said.

Officials have linked 84 cases of the potentially deadly liver disease to the clinic and have notified 50,000 patients that they may be at risk. Another case was linked to a sister clinic.