Bose-Einstein correlations of both neutral and like-sign charged pion
pairs are measured in a sample of 2 million hadronic $\mathrm{Z}$
decays collected with the L3 detector at LEP. The analysis is
performed in the four-momentum difference range
$300 \mathrm{\ Me\kern -0.1em V} < Q < 2 \mathrm{\ Ge\kern -0.1em V}$.
The radius of the neutral pion source is found to be smaller than that
of charged pions. This result is in qualitative agreement with the
string fragmentation model.