  Lyman Alpha Emitters (LAEs) are usually thought to be powered by star
formation. It has been recently reported that a fraction of LAEs at redshift
z~3-4 hosts an Active Galactic Nuclei (AGN). If an AGN is present it could be
obscured and undetectable in X-rays, but yet dominate the Lya luminosity. We
examine the properties of these AGN-powered LAEs at high redshift (z>=6) using
radiative transfer cosmological simulations and obtain a reliable criterion to
identify them from their observed \Lya line and surface brightness. We find
that these sources should have: (a) negative line weighted skewness, S_w <0,
and (b) surface brightness profiles FWHM >= 1.5". This parameter space cannot
be populated by starburst LAEs. Thus, LAEs satisfying this criterion would be
strong candidates for the presence of a hidden AGN powering their luminosity.
