Through our MPE guaranteed-time program, a picture has emerged that
most of the Ultraluminous IR galaxies (ULIRGs, L_ir > 10^12 L_sun)
observed so far seem to be mainly powered by starbursts instead of
AGNs.  However, a subset of ULIRGs, so-called Ultraluminous WARM IR
galaxies, seems to be an exception in the sense that these ULIRGs
might actually be powered by AGNs.  By examing its brighest member
with Seyfert2 characteristics, we will investigate whether this class
of ULIRGs is really powered by dust-enshrouded AGNs.  If this is
confirmed, we will be forced to consider the population of ULIRGs as a
mixed bag of various types of galaxies powered by different processes
instead of a homogeneous population of galaxies powered by the same
mechanism.