We present 6 cm VLA observations of nine regions with molecular or HH outtows, that appear to be driven by young stellar objects of low bolometric luminosity. Radio continuum emission at 3.6 cm had been previously detected toward the center of symmetry of 13 outtows in these regions. With the new 6 cm observations we have been able to estimate the spectral index in the 6 cm to 3.6 cm wavelength range for 11 of these outtow central (Class 0 and Class I) sources. All the spectral indices obtained for these central sources are positive, and consistent with partially thick thermal free-free emission. We discuss this result in relation to the current models for the origin of cm radio continuum emission in outtow sources. In particular, we nd that the observed ux densities of these sources t very well in the observational correlation between the radio continuum luminosity and the momentum rate of the outtow (e. g., Anglada 1996), and that the results are consistent with the central sources being thermal radio jets. Our data suggest that the ionized part of the jets begins at a distance < 10 AU from the star. In addition, we have derived a positive value for the spectral index of the Herbig-Haro object 32A, indicative of partially thick thermal emission. For the remaining sources detected in the nine elds observed, our results indicate that the emission is, in general, non-thermal as expected for background extragalactic sources. However, a few of these sources could be related to the star-forming regions studied.