  We report on the filament of ionized gas found at the NE periphery of M87,
the second brightest elliptical galaxy in the Virgo cluster. The object lies at
3.16 arcmin (15.7 kpc) projected distance of the nucleus of M87, and it
coincides in position with the Eastern radio lobe of M87. Long slit
spectroscopy confirmed the gaseus nature of this object, showing Hbeta, [OIII],
[OI], [NII], Halpha and [SII] lines, without any underlying continuum. The
redshift of the object, V = 1170+-25 km/s, agrees with the velocity of M87
itself (V = 1280 km/s), and with the bulk of the ionized material found near
the center of M87. The Halpha flux of this filament corresponds to 1 % of the
ionized material in M87. The radio-optical coincidence together with the
spectral characteristics suggest that the filament is ionized by a shock.
