A non-invasive system for detection of explosives and contraband in a vehicle includes at least one laser vibrometer for measuring vehicle vibrations at one or more points on the vehicle while the vehicle is operating. One laser vibrometer can be sequentially directed to various points on the vehicle according to a predetermined single point or pattern. Or, a plurality of laser vibrometers could be used to simultaneously illuminate the vehicle. After measurement, the vehicle vibrations are compared to a database of reference vibrations, which that were taken of similar vehicles that were known to be contraband-free. The measured vibrations are compared to the vibrations pattern for the same type of vehicle. If the vibration patterns exhibit differences in frequency peaks that exceed predetermined parameters, the system alerts the operator. A more detailed inspection of the vehicle can then be accomplished.