In a major crackdown, the Narcotics Control Bureau (NCB) on Saturday busted a drug trafficking racket by arresting three persons and recovering 20 kg of mephedrone, worth Rs 50 crore, cash and gold ornaments in search operations, an official said on Saturday. The crackdown was carried out after the NCB's Mumbai zonal unit received information about a drug syndicate operating out of Dongri area, involved in trafficking and distributing mephedrone in various parts of the city.