The Indian police on Thursday filed a case against a doctor suspected to have been involved in a multi-billion dollar kidney transplant racket and began probing the death of three Turkish nationals at his hospital in a northern Indian town, news reports said, according to dpa. Aggarwal was arrested on January 24 at his hospital in Ballabhgarh, about 20 kilometres south of Delhi, after raids on several clinics in the outskirts of the Indian capital believed to be at the centre of the racket, PTI and IANS news agencies reported. Aggarwal is one of the four doctors, including prime suspect Amit Kumar, who allegedly ran the illegal trade in which more than 500 poor labourers were duped into parting with their kidneys which were sold to wealthy clients from India and abroad over a period of eight to nine years. The police suspect the transplant racket served international clients from Britain, the United States, Greece, Turkey, Lebanon, Canada, Saudi Arabia and Dubai. Kumar has fled, with police believing him to have gone either to Canada or Nepal. Ballabhgarh police registered a case against Aggarwal on Wednesday in connection with the death of three Turkish men who were being treated for kidney ailments at his hospital between 2003 and 2005 on the suspicion that they may have been transplant clients, PTI and IANS reported. Aggarwal said the three men had died of cardiac arrest. "We have registered a case and are investigating," a senior police official said. The Turkish embassy had asked the Indian government to look into the deaths in 2006. The government of Haryana state, where Ballabhgarh is located, set up a medical enquiry that reported medical negligence and irregularities and also noted that no post-mortem examinations were conducted on the deceased. The probe team suggested further investigations, but no action was taken.