Purpose – The purpose of this paper is to examine the localisation of ferromagnetic objects buried in the underground. More specifically, it deals with the reconstruction of the XY-positions, the depths (Z-positions), the number, and the extension of the objects based on geomagnetic measurements. This paper introduces a minimum-norm reconstruction approach and evaluates its performance in a simulation study. Design/methodology/approach – Aminimum-L2-norm estimation based on the truncated singular value decomposition method with lead field weighting is proposed in order to localise geomagnetic sources. The sensor setup and positions are taken from real measurements. The source space is formed by an automatically generated grid. At each grid point, a magneto-static dipole is assumed. Findings – Sources with different depths and XY-positions could be successfully reconstructed. The proposed approach is not overly sensitive to errors/noise in measurement values and sensor positions. Originality/value – The approach described in this paper can be used for applications like geoprospection, archaeology, mine clearing, and the clean-up of former waste deposits.