There is provided an apparatus for monitoring a condition of an elongated ferrous object having a longitudinal axis, said apparatus including at least one magnetizing circuit including magnetic poles separated along the longitudinal axis, and magnetic field sensors arranged at the poles, said poles including pole shoes for directing magnetic flux between the poles and the monitored object. The pole shoes include openings between the monitored object and the poles, an opening including two ends separated in a direction perpendicular to the longitudinal axis by a mid-section defining a smaller opening than the ends for concentrating the magnetic flux at the mid-section. There is further provided an arrangement including one or more elongated objects for hoisting payload, wherein the monitoring apparatus is attached to the elongated objects.