A statistical model of the early stage of central nucleus-nucleus (A+A) col
lisions is developed. We suggest a description of the confined state with s
everal free parameters fitted to a compilation of AS-A data at the AGS. For
the deconfined state a simple Bag model equation of state is assumed. The
model leads to the conclusion that a Quark Gluon Plasma is created in centr
al nucleus-nucleus collisions at the SPS. This result is in quantitative ag
reement with existing SPS data on pion and strangeness production and gives
a natural explanation for their scaling behaviour. The localization and th
e properties of the transition region are discussed. It is shown that the d
econfinement transition can be detected by observation of the characteristi
c energy dependence of pion and strangeness multiplicities, and by an incre
ase of the event-by-event fluctuations. An attempt to understand the data o
n J/psi, production in Pb+Pb collisions at the SPS within the same approach
is presented.