We present the analysis of ASCA archival data from the Galactic source W51 .
The ASCA spectra show that the soft ( kT \lower 2.15 pt \hbox { $ \buildrel < \over { \sim } $ } 2.5 keV ) X-rays are of thermal origin and are compatible with W51C being a single , isothermal ( kT \simeq 0.3 keV ) supernova remnant at the far-side of the Sagittarius arm .
The ASCA images reveal hard ( kT \lower 2.15 pt \hbox { $ \buildrel > \over { \sim } $ } 2.5 keV ) X-ray sources which were not seen in previous X-ray observations .
Some of these sources are coincident with massive star-forming regions and the spectra are used to derive X-ray parameters .
By comparing the X-ray absorbing column density with atomic hydrogen column density , we infer the location of star-forming regions relative to molecular clouds .
There are unidentified hard X-ray sources superposed on the supernova remnant and we discuss the possibility of their association .