  The strong coupling diagram technique is used for investigating states near
the metal-insulator transition in the half-filled two-dimensional repulsive
Hubbard model. The nonlocal third-order term is included in the irreducible
part along with local terms of lower orders. Derived equations for the electron
Green's function are solved by iteration for moderate Hubbard repulsions and
temperatures. Starting iteration from Green's functions of the Hubbard-I
approximation with various distances of poles from the real frequency axis
continua of different metallic and insulating solutions are obtained. The
insulating solutions vary in the width of the Mott gap, while the metallic
solutions differ in the shape of the spectral function in the vicinity of the
Fermi level. Besides, different scenarios of the metal-insulator transition --
with a sudden onset of a band of mobile states near the Fermi level and with
gradual closure of the Mott gap -- are observed with a change in temperature.
In spite of these dissimilarities, all solutions have a common curve separating
metallic and insulating states in the phase diagram. Near this curve metallic
and insulating solutions coexist. For moderate Hubbard repulsions metallic
solutions are not Fermi liquids.
