Delta Air Lines said today that 19 of 21 passengers transported to local hospitals after a Toronto plane crash a day earlier have been released, as officials continue a probe into why the regional jet flipped over on landing.

Greater Toronto Airports CEO Deborah Flint said at a press conference that the two remaining hospitalized passengers did not face life-threatening injuries.

“It’s really, really incredible when you see that aircraft — it just makes you really thankful for all the safety checks,” Flint said, praising the flight crew and first responders.

A team of investigators from Canada’s Transportation Safety Board are leading the probe into the CRJ900 aircraft operated by Delta Air Lines’ Endeavor Air subsidiary went belly-up on Monday at Toronto’s Pearson Airport. They are getting assistance from the U.S. National Transportation Safety Board and the Federal Aviation Administration.

It’s not yet clear what happened to Flight 4819 from Minneapolis-St. Paul International Airport. Air crashes are usually caused by multiple factors.

The 16-year-old CRJ900, made by Canada’s Bombardier and powered by GE Aerospace engines, can seat up to 90 people. At least one of the two wings was no longer attached to the plane, video showed after the accident.

Toronto Pearson Airport said earlier on Monday it was dealing with high winds and frigid temperatures as airlines attempted to rebound after a weekend snowstorm dumped more than 8.6 inches of snow.

The wreckage of the plane is expected to remain on the airport grounds for potentially another 48 hours and two of Pearson’s runways will remain closed until it is removed, Flint said.

The Delta plane touched down in Toronto at 2:13 p.m. (1913 GMT) after an 86-minute flight and came to rest near the intersection of Runway 23 and Runway 15, FlightRadar24 data showed.

The weather at the time of the crash indicated a “gusting crosswind and blowing snow,” the flight tracking website said.