  We studied spatial distribution of dynamic nuclear polarization (DNP) in a
Hall-bar device in a breakdown regime of the quantum Hall effect (QHE). We
detected nuclear magnetic resonance (NMR) signals from the polarized nuclear
spins by measuring the Hall voltage $V_{xy}$ using three pairs of voltage
probes attached to the conducting channel of the Hall bar. We find that the
amplitude of the NMR signal depends on the position of the Hall voltage probes
and that the largest NMR signal is obtained from the pair of probes farthest
from the electron-injecting electrode. Combined with results on pump-and-probe
measurements, we conclude that the DNP induced by QHE breakdown develops along
the electron-drift direction.
