  We re-analyze the results of the searches for Heavy Neutral Leptons (HNLs) by
the CHARM experiment. We study HNL decay channel $N\to
e^{+}e^{-}\nu/\mu^{+}\mu^{-}\nu$ 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
$380 \text{ MeV}<m_{N}\lesssim 1.6\text{ GeV}$ - the region in the parameter
space that was considered in the literature as a target for HNLs searches.
