  A search for massive neutrinos has been made in the decay $\pi\rightarrow e^+
\nu$. No evidence was found for extra peaks in the positron energy spectrum
indicative of pion decays involving massive neutrinos ($\pi\rightarrow e^+
\nu_h$). Upper limits (90 \% C.L.) on the neutrino mixing matrix element
$|U_{ei}|^2$ in the neutrino mass region 60--135 MeV/$c^2$ were set, which are
%representing an order of magnitude improvement over previous results.
