  Spiral galaxies appear to be dynamical systems whose disks are still forming
at the current epoch and which continue to accrete mass. The presence of
extraplanar gas in spirals indicates that galactic halos can contain at least
part of the material needed to fuel the star formation activity in their disks.
Here we present the analysis of the ALFALFA survey data in the region of M33
aimed at searching high velocity clouds around this Local Group galaxy. We find
a varied population of HI clouds with masses ranging between 4 x 10^4 and few
times 10^6 M_sun. We also detect an extended HI complex at anomalous
velocities, whose extragalactic nature cannot be firmly established. We
estimate that the total amount of neutral hydrogen mass associated to these
clouds is around 10^7 M_sun.
