Video of the Toronto plane crash shows evacuees exiting the Delta aircraft with their luggage as a flight attendant can be heard saying, "Leave everything. Drop it."

"While it was happening, I very calmly had the thought that I was likely going to die," the Delta Air Lines passenger recalled.

An investigation is underway into the Delta plane that crash-landed Monday in Toronto. What caused it remains to be seen, but here's what we know so far.