We reanalyze the results of the searches for Heavy Neutral Leptons (HNLs) by the CHARM experiment. We study HNL decay channel N -> e(+) e(-)nu/mu(+) mu(-)nu and show that, in addition to the constraints on the HNL's mixings with nu e or nu(mu), the same data also implies limits on the HNLs that mix only with nu(tau) and have masses in the range 290 MeV < m(N) less than or similar to 1.6 GeV: the region in the parameter space that was considered in the literature as a target for HNLs searches.