The Nevada State Board of Medical Examiners had requested Dipak K Desai, owner of the Endoscopy Center of Southern Nevada where six cases of Hepatitis have been confirmed, to voluntarily stop practicing medicine, until the Board's investigation into allegations has been completed.

The Board said Desai had agreed to surrender his license, pending a probe into the centre's operations but did not give a timeframe as to how long the investigation may take.

A second Indian doctor linked to the scandal Vishvinder Sharma also resigned from the State Medical Board but did not turn over his medical license, local media reports said.

The FBI has also joined the investigation of the Endoscopy Center for possible Medicare fraud. Investigators want to know whether the center billed Medicare for 30-minute appointments that did not last that long.

The clinic may have also committed fraud for billing Medicare for two vials in instances when only one was used, officials said.

As many as 40,000 people may have been infected with the deadly Hepatitis C virus or HIV from the clinic over the last four years, officials said, adding six of Desai's facilities have been closed.