Investigators probing Monday's Delta plane crash at Toronto Pearson International Airport are piecing together what caused the dramatic incident.

One passenger said he was “drenched with jet fuel” as the planed rolled upside down and another claimed the crash occurred due to the flight crew’s "inadequate training," according to the lawsuits.

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.