Rawat's detention comes as Delhi police are also probing some of their own officers for reportedly taking bribes to cover up the scam.
Police in the dock
One senior policeman has been arrested and six others are being tracked, as media reports claim they had accepted $50,000 (two million rupees) in bribes from Kumar.
Dubbed "Doctor Horror" by Indian newspapers, Kumar is said to have made millions of dollars by selling kidneys to wealthy Indians and foreigners for transplant purposes.
He has been charged with causing grievous hurt with a weapon, wrongful confinement and fraud for allegedly luring or forcing hundreds of poor people into giving up their organs.
Live kidney transplants are allowed in India only if the organ is donated by a blood relative or spouse, or if there is a swap agreement between two needy families. All transplants must be cleared by the government.
But a huge gap in demand and poor availability of kidneys from dead donors has led to a thriving underground business.