  We report molecular line and dust continuum observations toward the high-mass
star forming region G331.5-0.1, one of the most luminous regions of massive
star-formation in the Milky Way, located at the tangent region of the Norma
spiral arm, at a distance of 7.5 kpc. Molecular emission was mapped toward the
G331.5-0.1 GMC in the CO (J=1-0) and C18O (J=1-0) lines with NANTEN, while its
central region was mapped in CS (J=2-1 and J=5-4) with SEST, and in CS (J=7-6)
and 13CO (J=3-2) with ASTE. Continuum emission mapped at 1.2 mm with SIMBA and
at 0.87 mm with LABOCA reveal the presence of six compact and luminous dust
clumps, making this source one of the most densely populated central regions of
a GMC in the Galaxy. The dust clumps are associated with molecular gas and they
have the following average properties: size of 1.6 pc, mass of 3.2x10^3 Msun,
molecular hydrogen density of 3.7x10^4 cm^{-3}, dust temperature of 32 K, and
integrated luminosity of 5.7x10^5 Lsun, consistent with values found toward
other massive star forming dust clumps. The CS and 13CO spectra show the
presence of two velocity components: a high-velocity component at ~ -89 km
s^{-1}, seen toward four of the clumps, and a low-velocity component at ~ -101
km s^{-1} seen toward the other two clumps. Radio continuum emission is present
toward four of the molecular clumps, with spectral index estimated for two of
them of 0.8+-0.2 and 1.2+-0.2. A high-velocity molecular outflow is found at
the center of the brightest clump, with a line width of 26 km s^{-1} (FWHM) in
CS (J=7-6). Observations of SiO (J=7-6 and J=8-7), and SO (J_K=8_8-7_7 and
J_K=8_7-7_6) lines provide estimates of the gas rotational temperature toward
this outflow >120 K and >75 K, respectively.
