  We investigate models for the power supply and broad-band spectral energy
distribution (SED) of hyperluminous IR galaxies, recently discovered at high
redshifts, in terms of the emission from an active nucleus embedded in a
torus-like dusty structure. We find consistent solutions in terms of a simple
torus model extended several hundreds of parsecs, with $A_V$ in the equatorial
plane of a few hundreds and a typical covering factor of over $50\%$. Objects
as different as the prototype high-z galaxy \fd, the z=0.93 IR object \fq, \fz\
found in a high-z cooling flow, and the optically selected BAL "Cloverleaf"
quasar, are all fitted by the same solution, for decreasing values of the polar
angle to the line-of-sight and proper scaling of the luminosities. We suggest
that such luminous high-z IR objects are heavily buried quasars surrounded by
large amounts of dust with high covering factors and large optical depths.
Comparison with UVX QSOs suggests that they are observed during a transient
phase. Forthcoming observations in the far-IR will soon allow probing this
phase and its relationship with the -- possibly concomitant -- formation of the
nuclear black hole and of the host galaxy.
