Twenty-four kilograms of ephedrine hydrochloride -- a psychotropic substance -- valued at Rs 50 million and used in making a chemical substitute of heroin was seized from the Kolkata house of former Central Bureau of Investigation official U N Biswas.

Biswas, who was the agency's additional director in charge of probing the fodder scam, had apparently rented the house to five foreigners -- three Myanmarese and two Chinese. But Biswas told PTI he had rented out his house to a Mizo, N Thanga, on the basis of a 'certificate' issued by the Mizoram government.

Narcotics Control Bureau Assistant Director (East) N C Patra said the raid was carried out after a tip-off from the United States Drug Enforcement Agency. NCB officers are questioning Biswas.

Patra said apart from the psychotropic substance, which is used for making amphetamine type stimulant, the NCB also seized laboratory equipment used for making the drugs.

Patra claimed the bust proves the presence of the powerful Myanmarese drug cartel in east India.

The arrested persons were sent to judicial remand till June 2 by a local court.