  X-ray-absorption fine-structure measurements at the Mn $K$-edge as a function
of temperature were performed on samples of La$_{1-x}$Ca$_x$MnO$_3$ and
La$_{0.67}$Pb$_{0.33}$MnO$_3$. All samples have a metal-insulator (MI)
transition near the ferromagnetic transition, except the Ca$_{0.5}$ sample,
which does not have a MI transition. Near $T_c$ for the MI samples, the
Debye-Waller $\sigma^2$ for the Mn-O atom-pair increases rapidly with
temperature. This non-thermal disorder is mostly along the direction of the
neighboring oxygens. These results strongly suggest small polarons which are
delocalized by a finite magnetization.
