  The construction of BRST invariant local operators with the quantum numbers
of the lightest glueball states, $J^{PC}= 0^{++}, 2^{++}, 0^{-+}$, is worked
out by making use of an Euclidean confining renormalizable gauge theory. The
correlation functions of these operators are evaluated by employing a confining
gluon propagator of the Gribov type and shown to display a spectral
representation with positive spectral densities. An attempt to provide a first
qualitative analysis of the ratios of the masses of the lightest glueballs is
also discussed
