State and county health officials said two of the patients already contracted hepatitis C, Newsday reported. The departments knew about the two cases for about 18 months, but didn't notify most of the other patients until Saturday, officials told the newspaper.

Claudia Hutton, a state health department spokeswoman, said the department had to complete its three-year investigation before it could notify the at-risk patients. A probe that began in 2004 found that for five years -- from 2000 to 2005 -- the doctor, an anesthesiologist, regularly used the same needle and syringe on multiple patients.

"He clearly was using incorrect infection control procedures," Hutton said.

The physician, who cooperated in the investigation, was allowed to practice after "being instructed on proper procedures," Hutton said, adding that the doctor will be monitored for three years by state and county health officials.

Officials said the Office of Professional Medical Conduct -- New York's disciplinary board for doctors -- closed a case against the doctor without any violations.