  We combine previously published interferometric and single-dish data of
relatively nearby massive dense cores that are actively forming stars to test
whether their `fragmentation level' is controlled by turbulent or thermal
support. We find no clear correlation between the fragmentation level and
velocity dispersion, nor between the observed number of fragments and the
number of fragments expected when the gravitationally unstable mass is
calculated including various prescriptions for `turbulent support'. On the
other hand, the best correlation is found for the case of pure thermal Jeans
fragmentation, for which we infer a core formation efficiency around 13 per
cent, consistent with previous works. We conclude that the dominant factor
determining the fragmentation level of star-forming massive dense cores at 0.1
pc scale seems to be thermal Jeans fragmentation.
