The alert system on a Delta Air Lines jet that flipped upside down and burst into flames as it tried to land in Toronto last month indicated a high rate of descent less than three seconds before touchdown, a preliminary report said Thursday. The Transportation Safety Board of Canada, which issu ed the report, continues to investigate the Feb. 17 crash-landing in which 21 people were hospitalized. All 76 passengers and four crew members survived when the Delta plane arriving from Minneapolis burst into flames after flipping over and skidding on the tarmac. The TSB of Canada report says that when the plane’s ground proximity warning system sounded 2.6 seconds before touchdown, the airspeed was 136 knots, or approximately 250 kph (155 mph). It says the plane’s landing gear folded into the retracted position at touchdown and the wing detached from the fuselage, releasing a cloud of jet fuel, which caught fire as the plane slid along the runway. The fuselage rolled upside down and a large portion of the tail came off in the process, the report says. “Accidents and incidents rarely stem from a single cause,” TSB chair Yoan Marier said in a video statement Thursday. “They’re often the result of multiple complex, interconnected factors, many extending beyond the aircraft and its operation to wider systemic issues.” The crew and passengers started evacuating once the plane came to a stop, the report says, adding that some of the passengers were injured when they unbuckled their seatbelts and fell to the ceiling. The TSB says it’s not aware of any issues with the seatbelts or seats during the incident. The cockpit door was jammed shut, forcing pilots to escape through the emergency hatch on the ceiling of the cockpit after everyone else was out, the report says. Emergency response personnel then went into the fuselage, and there was an explosion outside the plane near the left wing root shortly afterward, the TSB says. The cause of the explosion has not yet been determined. So far, the investigation has found no pre-existing problems with the flight controls, though some components were damaged in the crash, the board said. The safety board says its ongoing investigation is focusing on several key areas, including metallurgical examination of the wing structure, landing techniques, pilot training and the passenger evacuation process. All of those who were hospitalized were released within days of the crash. At least two lawsuits have been filed in the United States, and a law firm in Canada has said that it’s been retained by several passengers. Delta declined to comment on the preliminary report. “We remain fully engaged as participants in the investigation led by the Transportation Safety Board of Canada. Out of respect for the integrity of this work that will continue through their final report, Endeavor Air and Delta will refrain from comment,” the airline said. This story was originally featured on Fortune.com ...read more read less