Toronto ? Investigators trying to determine why an Air France jet skidded off a runway said Saturday that only four of the aircraft’s eight doors and emergency exits were used to escape the burning jetliner, and that two emergency slides malfunctioned.

Real Levasseur of Canada’s Transportation Safety Board said one of the four exit doors used by the 309 passengers and crew in their rush to disembark was difficult to open, and that the fire after the crash last Tuesday may have prevented access to the other doors.

Levasseur also said two of the slides used failed to work, even though they are supposed to automatically unfold when the emergency doors are opened.

The discovery confirms comments by many passengers and witnesses who said some of the slides and emergency exists were not functioning, forcing people to jump from as high as 4 or 5 yards. Some aviation experts have surmised that the impact of the Airbus A340, which slammed into a ravine, might have damaged the exit doors and chutes.