The purpose of this work is to do a systematic, deep search for sub-stellar objects orbiting nearby white dwarfs (WDs). The scientific interest spans testing specific predictions of models of common envelope phase, as well as providing constraints to planetary system evolution in advanced stages of its parent star. Additionally, we seek to explore the hypothesis about the origin of metal lines in hydrogen WDs, produced by the accretion of tidal disturbed asteroidal or cometary material. This could be linked to the presence of a planetary object. Here, we show preliminary results of our near-infrared astrometric project.