  The cosmological model consisting of a nonlinear magnetic field obeying the
Lagrangian L= \gamma F^{\alpha}, F being the electromagnetic invariant, coupled
to a Robertson-Walker geometry is tested with observational data of Type Ia
Supernovae, Long Gamma-Ray Bursts and Hubble parameter measurements. The
statistical analysis show that the inclusion of nonlinear electromagnetic
matter is enough to produce the observed accelerated expansion, with not need
of including a dark energy component. The electromagnetic matter with abundance
$\Omega_B$, gives as best fit from the combination of all observational data
sets \Omega_B=0.562^{+0.037}_{-0.038} for the scenario in which \alpha=-1,
\Omega_B=0.654^{+0.040}_{-0.040} for the scenario with \alpha=-1/4 and
\Omega_B=0.683^{+0.039}_{-0.043} for the one with \alpha=-1/8. These results
indicate that nonlinear electromagnetic matter could play the role of dark
energy, with the theoretical advantage of being a mensurable field.
