On vector bundles over moduli spaces trivial on Hecke curves

Let $M_X(r,\xi)$ be the moduli space of stable vector bundles, on a smooth complex projective curve $X$, of rank $r$ and fixed determinant $\xi$ such that $°(\xi)$ is coprime to $r$. If $E$ is a vector bundle $M_X(r,\xi)$ whose restriction to every Hecke curve in $M_X(r,\xi)$ is trivial, we prove that $E$ is trivial.