  A two-dimensional electron system interacting with an impurity and placed in
crossed magnetic and electric fields is under investigation. Since it is
assumed that an impurity center interacts as an attractive $\delta$-like
potential a renormalization procedure for the retarded Green's function has to
be carried out. For the vanishing electric field we obtain a close analytical
expression for the Green's function and we find one bound state localized
between Landau levels. It is also shown by numerical investigations that
switching on the electric field new long-living resonance states localized in
the vicinity of Landau levels can be generated.
