  The results of Mopra molecular spectral line observations towards the
supernova remnant HESSJ1731-347 (G353.6-0.7) and the unidentified gamma-ray
source HESSJ1729-345 are presented. Dense molecular gas in three different
velocity-bands (corresponding to three Galactic arms) are investigated using
the CS(1-0) line. The CS-traced component provides information about the dense
target material in a hadronic scenario for gamma-ray production (cosmic rays
interacting with gas) and an understanding of the dynamics. Furthermore, the
effects of cosmic ray diffusion into dense gas may alter the gamma-ray spectrum
to cause a flattening of spectra towards such regions. Dense molecular gas mass
at a level of ~10^5 Mo was revealed in this survey, with mass of the order of
~10^3 Mo towards HESSJ1729-345 in each coincident Galactic arm, but no
significant detection of dense molecular gas towards HESSJ1731-347 at the
currently-preferred distance of ~5.2-6.2 kpc was discovered.
