Based on the reports coming out now, it's looking more and more like the aircraft had a cargo fire on approach, ran off the runway during rollout (probably when the nose gear collapsed), and burnt out.
Looking at the various photos circulating, the fuselage appears to have broken just aft of the wing, and with no sign of fire outside the aircraft (which would suggest ruptured fueltanks), and no visible damage other than the collapsed nosegear and fire damage, these all support the cargo fire theory.
Yorden