The trio -- identified as Devendra Sen (29), Ram A Tyagi (27) and Nepalese national Vikrant Gurung (27) -- have been arrested under the Narcotic Drugs and Psychotropic Substances (NDPS) Act, officials said.
Sen, they said, is a medical representative working in Agra and the two others are his friends.
The operation was a result of intelligence gathered by the agency about a narcotics and charas (cannabis) racket being operated from India to European and East Asian countries, NCB Zonal Director (Delhi) Madho Singh said.
The 6.5 kg charas concealed in it was seized, the officer said.
The contraband, he said, used to be sent on public transport buses that come to India from Nepal.
The Nepalese kingpin and others associated in the drugs ring across various countries are being investigated, he said.