The CBI on Monday filed charge sheet against Ravi Krishna, director of Ziqitza Health Care Pvt Ltd and son of former minister Vayalar Ravi, its CEO and others in connection with alleged corruption in the operation of ambulances in Rajasthan after three years of probe.

The agency has also named Krishna, CEO Sweta Mangal and employee Amit Antony Alex, and the company Ziqitza Health Care as accused in the charge sheet, the officials said.

The FIR registered by the state government had named former chief minister Ashok Gehlot and alleged directors of the company, Congress leader Sachin Pilot, Karti Chidambaram (son of former union minister P. Chidambaram), Ravi Krishna (son of former union minister Vayalar Ravi), Ziqitza Health Care, Mangal, the then health minister of the state Duru Mirza, and the director of the National Rural Health Mission.

However, the charge sheet filed after three years of investigation on Monday does not name Gehlot, Pilot, Chidambaram or Mirza as accused.

The officials said the investigation is continuing and further charge sheets will be filed on the basis of evidence which may be gathered in the course of time, they said.

"The charge sheet has been filed in the competent court, Jaipur on the allegations related to irregularities in the operation of ambulances in Rajasthan," CBI spokesperson R.K. Gaur said.

After filing of the FIR, Pilot had said he had resigned from the company in late 2002 or early 2003 (before he became MP) when it decided to become a for profit company from the non-profit venture as he was associated with it only for social cause.

The CBI has claimed that the period of the alleged crime is between 2010-13. It is alleged in the case that ambulance services of 108 number were set up in the erstwhile Vasundhara Raje government which were provided by EMR company.

When the Raje government returned to power, a police complaint was filed before the Jaipur police, they said, adding the state government wrote asking the CBI to take over the probe.

The case was registered by the state police on the basis of allegations levelled by some politicians which was taken over by the CBI.

The complainant had alleged that when the Gehlot government came they found alleged irregularities in the services and recommended that fresh tenders be called for plying ambulances in the state.

CBI sources said it is alleged the terms of tenders were tweaked in such a way (making it mandatory for the ambulances to have GPS among others) that it favoured Ziqitza Health Care making it the sole bidder.