Lufthansa Cargo said on Jul 30th, that they have no indication of an inflight fire.
GACA's head of the aviation safety department Abel Rahman Bukhari said on Jul 31st, that preliminary investigation results suggest, that there was no inflight fire prior to touch down. The undercarriage of the aircraft was severly damaged in the landing causing the airplane to veer off the runway. The impact caused the fire on board.
The NTSB reported on Jul 31st, that the aircraft "reportedly caught fire after a hard landing at the King Khalid International Airport, Riyadh, Saudi Arabia"