The fate of massive cold clumps , their internal structure and collapse need to be characterised to understand the initial conditions for the formation of high-mass stars , stellar systems , and the origin of associations and clusters .
We explore the onset of star formation in the 75 M _ { \sun } SMM1 clump in the region ISOSS J18364-0221 using infrared and ( sub- ) millimetre observations including interferometry .
This contracting clump has fragmented into two compact cores SMM1 North and South of 0.05 pc radius , having masses of 15 and 10 M _ { \sun } , and luminosities of 20 L _ { \sun } and 180 L _ { \sun } .
SMM1 South harbours a source traced at 24 and 70 \micron , drives an energetic molecular outflow , and appears supersonically turbulent at the core centre .
SMM1 North has no infrared counterparts and shows lower levels of turbulence , but also drives an outflow .
Both outflows appear collimated and parsec-scale near-infrared features probably trace the outflow-powering jets .
We derived mass outflow rates of at least 4 \times 10 ^ { -5 } M _ { \sun } yr ^ { -1 } and outflow timescales of less than 10 ^ { 4 } yr. Our HCN ( 1-0 ) modelling for SMM1 South yielded an infall velocity of 0.14 km s ^ { -1 } and an estimated mass infall rate of 3 \times 10 ^ { -5 } M _ { \sun } yr ^ { -1 } .
Both cores may harbour seeds of intermediate- or high-mass stars .
We compare the derived core properties with recent simulations of massive core collapse .
They are consistent with the very early stages dominated by accretion luminosity .