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    PR # 31126                                                                   
       Discovery of the ultra-luminous infrared galaxies (ULIRGs) has prov       
     ided  a clue to an evolutionaly connection between starburst and  act       
     ive galactic nuclei. Nearly all ULIRGs with flat infrared slope  show       
      optical spectra with high excitation condition similar to those of A       
     GNs.  Sanders et al. (1988) showed change of the IRAS color could be        
      a possible trace of the evolution from starburst dominated phase  to       
      gas-dust enshrouded AGN stage. We selected 100 micron bright galaxie       
     s with L(IR) 10**12Lo  for two distinct classes: ``cold'' and ``warm'       
     ' sample  based on the IRAS color.Strong X-ray emission is a crucial        
     evidence  for presence of AGN.By comparison of X-ray nature between         
     the two samples, a genesis of AGN in the powerful infrared galaxy  ca       
    n be tested.                                                                 
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