Silicon Valley (PTI): Authorities have "flagged" the passport of Dipak Desai, the Indian-American owner of a Las Vegas clinic chain that is at the centre of one of the biggest malpractices scandal in the US, with the police saying the probe "is not far enough" to charge the doctor.

Although flagging of Desai's passport will not prevent him from leaving the country, it would notify law enforcement officials and allow them to interview Desai before he leaves the US, according to sources close to the investigation.

The scandal came to light last month after it was alleged that the staff were reusing medical supplies including syringes and vials at his Endoscopy Center, triggering a major healthscare.

It prompted authorities to notify about 40,000 patients that they should be tested for hepatitis B, hepatitis C and HIV. Desai's Endoscopy Centre of Southern Nevada was closed after officials confirmed that six people had been infected with hepatitis C because of unsafe medical practices at the clinic.

Metro Police Deputy Chief Kathy Suey said Desai is "absolutely one of the persons we're looking at in the investigation," reported the Las Vegas Sun newspaper.

However, that investigation "is not far enough to charge him with something" at this time, Suey added.

It was unclear whether it was the local or the federal agencies that had requested the action in regard to Desai's passport, the paper said.

Desai's attorney, Richard Wright, refused to comment on his client's passport being flagged, the paper reported.

He also refused to confirm authorities' belief that his client is still in Las Vegas, saying it is a private matter.