Sleuths of the Delhi zonal unit of the NCB seized drugs pseudoephedrine and ephedrine weighing over 32 kgs in three separate operations launched by them since yesterday.
All the four have been apprehended from the Indira Gandhi International Airport (IGIA) in the last 24 hours while they were trying to fly out to various foreign destinations with the contraband concealed in their bags, a senior NCB officer said.
The three women have been identified as Zambian Doris Mwansa (46), South Africans Mandaba Violet Xaba (31) and Patricia S Ncube (46), while the Nigerian man is Johnson, the officer said.
They have been arrested under sections of the Narcotic Drugs and Psychotropic Substances Act (NDPS).
"About 32.4 kgs of drugs worth Rs 70 lakh in the international market has been seized from the four in three different operations being conducted since yesterday," the officer said.
The contacts of the arrested foreigners in India are being investigated, he said.