  The crossover from orthogonal to the unitary universality classes in the
distribution of the anomalously localized states (ALS) in two-dimensional
disordered conductors is traced as a function of magnetic field. We demonstrate
that the microscopic origin of the crossover is the change in the symmetry of
the underlying disorder configurations, that are responsible for ALS. These
disorder configurations are of weak magnitude (compared to the Fermi energy)
and of small size (compared to the mean free path). We find their shape
explicitly by means of the direct optimal fluctuation method.
