  We report results of a numerical study of noninteracting electrons moving in
two dimensions, in the presence of a random potential and a random magnetic
field for a sequence of finite sizes, using topological properties of the wave
functions to identify extended states. Our results are consistent with the
existence of a second order localization-delocalization transition driven by
the random potential. The critical randomness strength and localization length
exponent are estimated via a finite size scaling analysis.
