  Understanding the reasons for the faintness of the optical/near-infrared
afterglows of the so-called dark bursts is essential to assess whether they
form a subclass of GRBs, and hence for the use of GRBs in cosmology. With VLT
and other ground-based telescopes, we searched for the afterglows of the
INTEGRAL bursts GRB 040223, GRB 040422 and GRB 040624 in the first hours after
the triggers. A detection of a faint afterglow and of the host galaxy in the K
band was achieved for GRB 040422, while only upper limits were obtained for GRB
040223 and GRB 040624, although in the former case the X-ray afterglow was
observed. A comparison with the magnitudes of a sample of afterglows clearly
shows the faintness of these bursts, which are good examples of a population
that an increasing usage of large diameter telescopes is beginning to unveil.
