Detection and recognition of taggant substances having predefined zero external field magnetic resonance signatures. An object comprising taggant substance(s) is irradiated with a sequence of specific excitation pulses of electromagnetic radiation within a predetermined time and frequency scanning pattern, responsive nuclear spin echo signals are received from the object with a predetermined time and frequency acquisition pattern and data indicative thereof is generated. The scanning and acquisition patterns used permit successive transmission of pulses of multiple frequencies using a two-pulse spin-echo excitation technique, or a steady state-spin echo excitation technique, and successive acquisition of multiple nuclear spin echo response signals, within a time slot between two successive excitation pulses of a specific excitation frequency. The generated data is correlated with reference data corresponding to predetermined taggant substance(s) and one or more taggant substances are identified based on the determined correlation.