Groups quasi-isometric to symmetric spaces

We determine the structure of finitely generated groups which are quasi-isometric to nonpositively curved symmetric spaces, allowing Euclidean de Rham factors. If X is a symmetric space of noncompact type (i.e. it has no Euclidean de Rham factor), and Γ is a finitely generated group quasi-isometric to the product double-struck E sign^k x X, then there is an exact sequence 1 → H → Γ → L → 1 where H . contains a finite index copy of ℤ^k and L is a uniform lattice in the isometry group of X.