  Sterile neutrinos with masses $\sim 0.1$ eV or higher would play an important
role in astrophysics and cosmology. We explore possible signatures of such
sterile neutrinos at long baseline experiments. We determine the neutrino
conversion probabilities analytically in a 4-neutrino framework, including
matter effects, treating the sterile mixing angles $\theta_{14}, \theta_{24},
\theta_{34}$, the deviation of $\theta_{23}$ from maximality,as well as
$\theta_{13}$ and the ratio $\Delta m^2_\odot/\Delta m^2_{atm}$ as small
parameters for a perturbative expansion. This gives rise to analytically
tractable expressions for flavor conversion probabilities from which effects of
these parameters can be clearly understood. We numerically calculate the
signals at a neutrino factory with near and far detectors that can identify the
lepton charge, and point out observables that can discern the sterile mixing
signals. We find that clean identification of sterile mixing would be possible
for $\theta_{24}\theta_{34} \gsim 0.005$ and $\theta_{14} \gsim 0.06$ rad with
the current bound of $\theta_{13} < 0.2$ rad; a better $\theta_{13}$ bound
would allow probing smaller values of sterile mixing. We also generalize the
formalism for any number of sterile neutrinos, and demonstrate that only
certain combinations of sterile mixing parameters are relevant irrespective of
the number of sterile neutrinos. This also leads to a stringent test of the
scenario with multiple sterile neutrinos that currently is able to describe all
the data from the short baseline experiments, including LSND and MiniBOONE.
