  We present results of general relativistic simulations of collapsing
supermassive stars with and without rotation using the two-dimensional general
relativistic numerical code Nada, which solves the Einstein equations written
in the BSSN formalism and the general relativistic hydrodynamics equations with
high resolution shock capturing schemes. These numerical simulations use an
equation of state which includes effects of gas pressure, and in a tabulated
form those associated with radiation and the electron-positron pairs. We also
take into account the effect of thermonuclear energy released by hydrogen and
helium burning. We find that objects with a mass of 5x10^{5} solar mass and an
initial metallicity greater than Z_{CNO}~0.007 do explode if non-rotating,
while the threshold metallicity for an explosion is reduced to Z_{CNO}~0.001
for objects uniformly rotating. The critical initial metallicity for a
thermonuclear explosion increases for stars with mass ~10^{6} solar mass. For
those stars that do not explode we follow the evolution beyond the phase of
black hole formation. We compute the neutrino energy loss rates due to several
processes that may be relevant during the gravitational collapse of these
objects. The peak luminosities of neutrinos and antineutrinos of all flavors
for models collapsing to a BH are ~10^{55} erg/s. The total radiated energy in
neutrinos varies between ~10^{56} ergs for models collapsing to a BH, and
~10^{45}-10^{46} ergs for models exploding.
