Observations of SN 1994W with British telescopes and NOT on La Palma showed
a steep decline of the light curve around 
days. This is
interpreted as due to a very low amount of ejected 
Ni, which for a
high mass progenitor could indicate fall-back of material onto a newly
formed black hole. Later, observations of SN 1997D showed a low Ni
abundance also for that supernova. SN 1997D is modelled as the explosion of
a 25 solar mass star, which again implies the formation of a very massive
compact object in the center. To investigate the late time emission of
core-collapse supernovae, a monitoring program has been conducted using the
large ESO telescopes at La Silla. The first supernova analyzed was SN
1996N. This well observed supernova provides clues to the relation between
supernovae of Type II and Type Ib/c. The observed blueshifts of the
emission lines could indicate large scale asymmetries in the supernova
explosion.