The doctors and few others were issued notices under CrPC Section 160, with the investigators asking them to join the probe into the matter at the earliest.
A Special Investigation Team questioned Ashok Sarin and D K Aggarwal, both nephrologists at Apollo Hospital, in connection with kidney transplants facilitated by the racket, yesterday evening. They were asked to come for another round of questioning today as well, a senior police official said.
Meanwhile, the police are also in the process of sending notices to three other senior doctors, who are members of the hospital's committee for verifying documents pertaining to transplants.
In a statement, Apollo Hospital said, "Indraprastha Medical Corporation Limited (Indraprastha Apollo Hospitals) has been a victim of a well-orchestrated operation carried out by a few individuals with malafide intent who deliberately committed forgery and fraud.
"The matter is under investigation by the Delhi Police and as in the past, the hospital continues to extend full cooperation to the investigating team. Additionally, we have advised the doctor, who has been asked to join the investigation, to extend full cooperation with the police.