  In a hydrodynamic model, we have analysed the direct photon data obtained by
the WA98 collaboration in 158 A GeV Pb+Pb collisions at CERN SPS. The
transverse expansion of the system was taken into account. Two scenarios (i)
formation of quark-gluon plasma and (ii) formation of hot hadronic gas were
considered. Equally well description to the data were obtained in both the
scenarios. However, hadronic gas scenario require very high initial temperature
($\sim$ 300 MeV) and it is difficult to conceive existence of hadron gas at
that high temperature. If the hadronic fluid has small radial velocity
(0.2c-0.3c) initially, the data are well explained in the hadronic gas scenario
with reasonable initial temperatures.
