Context : The process of high-mass star formation is still shrouded in controversy .
Models are still tentative and current observations are just beginning to probe the densest inner regions of giant molecular clouds .

Aims : The study of high-mass star formation requires the observation and analysis of high density gas .
This can be achieved by the detection of emission from higher rotational transitions of molecules in the sub-millimeter .
Here , we studied the high-mass clump G30.79 FIR 10 by observing molecular emission in the 345 GHz band .
The goal is to understand the gravitational state of this clump , considering turbulence and magnetic fields , and to study the kinematics of dense gas .

Methods : We approached this region by mapping the spatial distribution of HCO ^ { + } ( J = 4 \rightarrow 3 ) , H ^ { 13 } CO ^ { + } ( J = 4 \rightarrow 3 ) , CS ( J = 7 \rightarrow 6 ) , ^ { 12 } CO ( J = 3 \rightarrow 2 ) , and ^ { 13 } CO ( J = 3 \rightarrow 2 ) molecular emission by using the ASTE telescope and by observing the ^ { 12 } C ^ { 18 } O ( J = 3 \rightarrow 2 ) , HCN ( J = 4 \rightarrow 3 ) , and H ^ { 13 } CN ( J = 4 \rightarrow 3 ) molecular transitions with the APEX telescope .

Results : Infalling motions were detected and modeled toward this source .
A mean infall velocity of 0.5 km s ^ { -1 } with an infall mass rate of 5 \times 10 ^ { -3 } M _ { \odot } /yr was obtained .
Also , a previously estimated value for the magnetic field strength in the plane of the sky was refined to be 855 \mu G which we used to calculate a mass-to-magnetic flux ratio , \lambda = 1.9 , or super-critical .
The virial mass from turbulent motions was also calculated finding M _ { \mathrm { vir } } = 563 M _ { \sun } , which gives a ratio of M _ { \mathrm { submm } } /M _ { \mathrm { vir } } =5.9 .
Both values strongly suggest that this clump must be in a state of gravitational collapse .
Additionally , we estimated the HCO ^ { + } abundance , obtaining X ( HCO ^ { + } ) = 2.4 \times 10 ^ { -10 } .

Conclusions :