A method for detecting threat materials used in explosives, comprising: receiving a sample of particulates suspected of containing explosive material from an unexploded state or an exploded state; selecting, based upon an output of a first optical interrogation device, an area of interest on the sample suspected of containing a threat material indicative of an explosive; predetermining that the threat material is a nitrate; interrogating, with an optical source, at least a portion of the area of interest with a Raman laser to produce a Raman spectrum, wherein the Raman spectrum is measured in a first spectral region, which is set to a wave number shift around 1050 cm -1; determining whether the area of interest includes the threat material by comparing an amplitude of the first spectral region of the Raman spectrum measured at approximately 1050 cm -1 during the interrogation, to a first predetermined threshold, where the predetermined threshold is set to a value corresponding to a feature in the first spectral range that is indicative of a nitrate; performing a verification, if the determination indicates that the area of interest includes the threat material, by checking for a secondary indicator of the presence of the threat material; and activating an indicator if the verification indicates that the sample contains the threat material; characterised in that the verification is performed by: interrogating at least a portion of the area of interest with a Raman laser to produce a Raman spectrum, wherein the Raman spectrum is measured in a second spectral region, which is set to a wave number shift around 3225 cm -1; comparing an amplitude of the second spectral region different from the first spectral region of the Raman spectrum measured during the interrogation, to a second predetermined threshold; and determining if the sample includes ammonium nitrate by comparing the amplitude of the measured portion of the Raman spectrum at approximately 3225 cm -1 to the second predetermined threshold, where the second threshold is set to a value corresponding to a feature in the second spectral region indicative of ammonium nitrate. receiving a sample of particulates suspected of containing explosive material from an unexploded state or an exploded state; selecting, based upon an output of a first optical interrogation device, an area of interest on the sample suspected of containing a threat material indicative of an explosive; predetermining that the threat material is a nitrate; interrogating, with an optical source, at least a portion of the area of interest with a Raman laser to produce a Raman spectrum, wherein the Raman spectrum is measured in a first spectral region, which is set to a wave number shift around 1050 cm -1; determining whether the area of interest includes the threat material by comparing an amplitude of the first spectral region of the Raman spectrum measured at approximately 1050 cm -1 during the interrogation, to a first predetermined threshold, where the predetermined threshold is set to a value corresponding to a feature in the first spectral range that is indicative of a nitrate; performing a verification, if the determination indicates that the area of interest includes the threat material, by checking for a secondary indicator of the presence of the threat material; and activating an indicator if the verification indicates that the sample contains the threat material; characterised in that the verification is performed by: interrogating at least a portion of the area of interest with a Raman laser to produce a Raman spectrum, wherein the Raman spectrum is measured in a second spectral region, which is set to a wave number shift around 3225 cm -1; comparing an amplitude of the second spectral region different from the first spectral region of the Raman spectrum measured during the interrogation, to a second predetermined threshold; and determining if the sample includes ammonium nitrate by comparing the amplitude of the measured portion of the Raman spectrum at approximately 3225 cm -1 to the second predetermined threshold, where the second threshold is set to a value corresponding to a feature in the second spectral region indicative of ammonium nitrate. interrogating at least a portion of the area of interest with a Raman laser to produce a Raman spectrum, wherein the Raman spectrum is measured in a second spectral region, which is set to a wave number shift around 3225 cm -1; comparing an amplitude of the second spectral region different from the first spectral region of the Raman spectrum measured during the interrogation, to a second predetermined threshold; and determining if the sample includes ammonium nitrate by comparing the amplitude of the measured portion of the Raman spectrum at approximately 3225 cm -1 to the second predetermined threshold, where the second threshold is set to a value corresponding to a feature in the second spectral region indicative of ammonium nitrate.