The four, including a couple, were arrested from the Kolkata's Anandapur area, ACP (Crime) Vishal Garg said at the Kolkata Police headquarters at Lalbazar.
"We have arrested four persons on the basis of an information that they were carrying drugs. During search, we recovered documents from them proving their involvement in a kidney racket operated from a private hospital," Mr Garg said.
Brown sugar weighing around 316 g with a market value of over Rs 3 lakh was allegedly seized from the accused identified as Ashfaque Ahmed, the kingpin of the racket, Tehrul Islam, Baidyanath Burman and his wife Joshna.
The hospital, however, denied that any kidney racket was operating from its establishment.
"With respect to reports on an alleged kidney racket, we would like to say that our documentation processes and procedures are among the best in the country. Each kidney transplant is done with government clearances after due diligence," a spokesperson of the hospital said.