Context : In recent years , we have detected clear evidence of rotation in more than 5 hot molecular cores ( HMCs ) .
Their identification is confirmed by the fact that the rotation axes are parallel to the axes of the associated bipolar outflows .
We have now pursued our investigation by extending the sample to 3 known massive cores , G10.62 - 0.38 , G19.61 - 0.23 , and G29.96 - 0.02 .

Aims : We wish to make a thorough study of the structure and kinematics of HMCs and corresponding molecular outflows to reveal possible velocity gradients indicative of rotation of the cores .

Methods : We carried out PdBI observations at 2.7 and 1.4 mm of gas and dust with angular resolutions of \sim 2 ^ { \prime \prime } –3 ^ { \prime \prime } , and \sim 1 ^ { \prime \prime } –2 ^ { \prime \prime } , respectively .
To trace both rotation and expansion , we simultaneously observed CH _ { 3 } CN , a typical HMC tracer , and ^ { 13 } CO , a typical outflow tracer .

Results : The CH _ { 3 } CN ( 12–11 ) observations have revealed the existence of clear velocity gradients in the three HMCs oriented perpendicular to the direction of the bipolar outflows .
For G19 and G29 the molecular outflows have been mapped in ^ { 13 } CO .
The gradients have been interpreted as rotating toroids .
The rotation temperatures , used to derive the mass of the cores , have been obtained by means of the rotational diagram method , and lie in the range of 87–244 K. The diameters and masses of the toroids lie in the range of 4550–12600 AU , and 28–415 M _ { \odot } , respectively .
Given that the dynamical masses are 2 to 30 times smaller than the masses of the cores ( if the inclination of the toroids with respect to the plane of the sky is not much smaller than 45 \degr ) , we suggest that the toroids could be accreting onto the embedded cluster .
For G19 and G29 , the collapse is also suggested by the redshifted absorption seen in the ^ { 13 } CO ( 2–1 ) line .
We infer that infall onto the embedded ( proto ) stars must proceed with rates of \sim 10 ^ { -2 } M _ { \odot } yr ^ { -1 } , and on timescales of the order of \sim 4 \times 10 ^ { 3 } –10 ^ { 4 } yr .
The infall rates derived for G19 and G29 are two orders of magnitude greater than the accretion rates indirectly estimated from the mass loss rate of the corresponding outflows .
This suggests that the material in the toroids is not infalling onto a single massive star , responsible for the corresponding molecular outflow , but onto a cluster of stars .

Conclusions :