Canadian investigator refused to comment on preliminary theories on what caused a passenger jet that flipped while landing in Toronto, Canada. “At this point, it’s far too early to say what the cause of this accident might be,” TSB Senior Investigator Ken Webster said in a video statement Tuesday, as he stood near the remains of the aircraft. He said investigators will examine the wreckage and runway, and have removed the cockpit voice and flight data recorders and sent them to the lab for analysis. The crash was the fourth major aviation accident in North America in the past three weeks. All 80 people on board the Delta Air Lines flight from Minneapolis that flipped Monday survived. Authorities said Tuesday that two people remain in the hospital while 19 others were treated for relatively minor injuries. Communications between the tower and pilot were normal on approach.