Police seized 39kg of brown sugar (a derivative of heroin), whose estimated cost on the clandestine market was around ₹40 crore, from a narcotics-processing unit that was operating on a mango plantation in Malda district on Tuesday night.

The operation was conducted by a team of the Golapganj investigation centre that functions under the Kaliachak police station.

The narcotics, police sources said, were packed in small cotton wrappings on the orchard in Shahabazpur.

During the raid, some people managed to escape, but the police could nab Barkat Sheikh, Rauf Sheikh and Hasibur Sheikh. Police officers are interrogating them to gather information about the racket that is involved in the processing and smuggling of narcotics.

“This is one of the most significant narcotics seizures in recent times,” said a senior police officer.

“Earlier seizures and arrests helped us piece together information about hidden drug-processing units. This time, our intelligence led us straight to the source,” he added.

During the investigation, the police found that the raw materials for brown sugar were sourced from Manipur and Jharkhand.

“These materials arrived in wet form, which were then dried and processed on-site on the plantation. The choice of the location, a secluded mango plantation, was a part of the plan to avoid suspicion from local people and authorities,” said the police officer.

The processed brown sugar was supposed to be sold across Malda as well as in the neighbouring states of Bihar and Jharkhand, sources said.