French aviation investigators arrived in Canada on Sunday amid questions over the cause of an apparent engine explosion that forced an Air France airliner to make an emergency landing.

Passengers reported hearing a loud bang on the Paris-Los Angeles flight, followed by vibrations that shook the cabin for 20 minutes.

By the time the Airbus A380 superjumbo jetliner landed at a military airfield in Goose Bay, Newfoundland on Saturday, the cowling covering one of the plane’s four engines had been completely torn off.