  We investigate the dispersion and the absorption properties of a weak probe
field in a three-level Lambda-type atomic system. We use just an incoherent
field for controlling the group velocity of light. It is shown that the slope
of dispersion changes from positive to negative just with changing the
intensity of the indirect incoherent pumping field. Gain-assisted superluminal
light propagation appears in this system. No laser field is used in the pumping
processes.
