  We present the first fully relativistic investigation of matter fallback in a
supernova. We investigate spherically symmetric supernova fallback using a
relativistic radiation hydrodynamics Lagrangian code that handles radiation
transport in all regimes. Our goal is to answer the fundamental question: did
SN1987A produce a black hole and, if so, when will the hole become detectable ?
We compute the light curve, assuming that a black hole has been formed during
the explosion, and compare it with the observations. Our preliminary
calculations lack radioactive energy input and adopt a very simple chemical
composition (pure hydrogen). As a result, our computed models cannot fit the
observed data of SN1987A in detail. Nevertheless, we can show that, during the
first hours, the accretion flow is self--regulated and the accretion luminosity
stays very close to the Eddington limit. The light curve is completely
dominated, during the first few weeks, by the emission of the stellar envelope
thermal energy, and resembles that obtained in ``standard'' supernova theory.
Only long after hydrogen recombination takes place is there even a chance to
actually detect radiation from the accreting black hole above the emission of
the expanding envelope. The presence of a black hole is thus not inconsistent
with observations to date. Because of the exponential decay of the $^{44}$Ti
radioactive heating rate, the date of the emergence of the black hole is not
very sensitive to the actual parameters of the models and turns out to be about
1000 years. The bulk of the emission then is expected to be in the visible
band, but will be unobservable with present instrumentation. We discuss the
implications of our results in connection with the possible emergence of a
black hole in other supernovae.
