A system and method for non-invasively inspecting one or more vessels capable of transmitting IR light containing liquid is provided, which uses a near-infrared (NIR) imaging device in combination with one or two NIR light sources, a diffuser plate, and an optical wavelength selecting means is provided for selecting one or more wavelength bands. In addition, the system may further comprise a computer processing means, a computer database containing known absorbance values, and a computer application, such that the system may compare the collected spectroscopic data to known spectroscopic data, and identify the liquid contained within the inspected vessel. The inspection method of the present invention measures a transmission or reflection image of one or more vessels being inspected at one or more narrow wavelength intervals in the NIR spectral range that corresponds to a peak absorbance wavelength of water, organic liquids, and explosive compositions.