Abstract: In a method and system for monitoring an underground cable in a site of interest, multiple samples of magnetic field data and corresponding location data are collected periodically over a sampling period of extended time. The magnetic field data samples and corresponding location data are processed to determine respective topologies of one or more current-carrying conductors in the site and for each of the conductors respective magnetic field data relating to each sampled point are integrated with respect to a predetermined parameter of the respective conductor so as compute an integrated contribution of each sampled span along the respective conductor. The data relating to different conductors in the site are output in a manner that allows determination of a conductor for which the parameter changes during the sampling period.