  We have measured cross sections for the $ (\pi^+,\pi^\pm p)$ reactions on
${\rm ^3H}$, ${\rm ^4He}$, ${\rm ^6Li}$ and ${\rm ^7Li}$ in quasi-free
kinematics at incident pion beam energy 500 MeV. An enhancement of the
$(\pi^+,\pi^- p)$ cross section in this kinematics is observed. If this is
interpreted as due to quasi-free scattering from pre-existing $\Delta$
components of the nuclear wave function, the extracted probabilities are in
agreement with theoretical expectations.
