In the biggest seizure in recent times, nearly 4 kg of cocaine, valued at Rs.40-50 crore in the international market, was seized from a South African woman at the Netaji Subhas Chandra Bose International Airport here, an official said on Wednesday.A Narcotics Control Bureau (NCB) official said 3.75 kg of cocaine was seized from the woman who flew into the city from Dubai on Tuesday.Acting on a tip off, the NCB personnel detained the woman at the international terminal and found the drug hidden in her bag."This haul is the biggest in recent times. In the international market, it can fetch anything between Rs.40 to 50 crore," the official said.A probe was on to find out why the cocaine was being brought to Kolkata and the intended recipient.