  We study the impact of primordial magnetic fields on the HI absorption from
the Epoch of Reionization. The presence of these fields result in two distinct
effects: (a) the heating of the haloes from the decay of magnetic fields owing
to ambipolar diffusion, and (b) an increase in the number of haloes owing to
additional matter fluctuations induced by magnetic fields. We analyse both
these effects and show that the latter is potentially observable because the
number of haloes along of line of sight can increase by many orders of
magnitude. While this effect is not strongly dependent on the magnetic field
strength in the range $0.3\hbox{--}0.6$ nG, it is extremely sensitive to the
magnetic field power spectral index for the near scale-free models. Therefore
the detection of such absorption features could be a sensitive probe of the
primordial magnetic field and its power spectrum. We discuss the detectability
of these features with the ongoing and future radio interferometers. In
particular, we show that LOFAR might be able to detect these absorption
features at $z \simeq 10$ in less than 10 hrs of integration if the flux of the
background source is 400 mJy.
