An official of the Drug Enforcement Agency of the United States will help Indian narcotics investigators probe a recent drug haul in Kolkata.

The Narcotics Control Bureau is seeking DEA's help because the latter has already handled investigations against the China-based Ah Hua cartel that is believed to be behind the Kolkata racket, busted on May 17.

NCB director (east) R M Meena in Kolkata said on Monday that the DEA official would arrive in New Delhi next week from China to track down the cartel members, some of whom had recently been arrested in New York and Beijing. 

The arrested Ah Hua gangsters had tipped off DEA interrogators about the racket's operations in Kolkata. NCB officials were in turn informed about this by DEA.

The raid on the house of U N Biswas, the former Central Bureau of Investigation additional director, revealed the presence of a rag-tag narcotics production unit on the ground floor that he had let out on rent.

Five foreigners -- three Myanmarese and two Chinese -- were arrested from the house for possessing 24kgs of ephedrine hydrochloride (heroine substitute) valued at Rs 50 million.

Biswas claimed the five foreigners were not his tenants and the person he had rented out a part of his house, S N Thanga, was missing. He appears to have fled to Myanmar and is also believed to be Ah Hua's key contact in India.