  We present high angular resolution interferometric observations of the 3 and
1.3mm continuum emission, and HCO+(1-0) and SiO(2-1)v=0 lines, obtained with
the Owens Valley Radio Observatory millimeter-wave array, toward two hot cores
(HCs) associated with two well known ultracompact (UC) HII regions: G29.96-0.02
and G31.41+0.31. These HCs are believed to host young forming massive stars
which have been suggested to be surrounded by massive rotating accretion disks.
The aim of these new observations is to study the structure and kinematics of
the molecular clumps surrounding the HCs and nearby UCHII regions at moderately
high angular resolution. Our observations reveal that the clumps within which
the HCs and UCHII regions are embedded have a complex kinematical structure.
The total mass of the clumps is estimated to be in the range 1000-3000 Msun,
consistent with previous findings. Our observations also show compelling
evidence that the clump in G29.96-0.02 is contracting onto the HC position,
suggesting that the accretion process onto the massive young stellar object
embedded in the HC is still ongoing. In these objects the kinematical structure
that we observe is also compatible with the presence of a massive rotating disk
within the HC, even though we cannot prove this suggestion with our data. The
case of G31.41+0.31 is more complicated, and our data, although consistent with
the presence of an inner disk and an infalling envelope around it, do not have
the required spatial resolution to resolve the different structures.
