  We compute the secondary CMBR anisotropy signal from the reionization of the
universe in the presence of tangled magnetic fields. We consider the tangled
magnetic-field-induced scalar, vector, and tensor modes for our analysis. The
most interesting signal for l<10 arise from tensor perturbations. In
particular, we show that the enhancement observed by WMAP in the TE
cross-correlation signal for l<10 could be explained by tensor TE
cross-correlation from tangled magnetic fields generated during the
inflationary epoch for magnetic field strength B_0=4.5*10^{-9}G and magnetic
field power spectrum spectral index n=-2.9. Alternatively, a mixture of tensor
mode signal with primordial scalar modes give weaker bounds on the value of the
optical depth to the reionization surface, tau_{reion}=0.11 +/- 0.02. This
analysis can also be translated to a limit on the magnetic field strength of
nearly 5*10{-9}G for wave-numbers < 0.05 Mpc^{-1}
