  We study the bifurcations of central configurations of the Newtonian
four-body problem when some of the masses are equal. First, we continue
numerically the solutions for the equal mass case, and we find values of the
mass parameter at which the number of solutions changes. Then, using the
Krawczyk method and some result of equivariant bifurcation theory, we
rigorously prove the existence of such bifurcations and classify them.
