A thread on FARK led me to the 1931 movie The Viking, which I was previously unfamiliar with. (This should not be confused with the 1928 movie The Viking.)
The Viking is somewhat interesting because it was the first talkie shot in Canada, because it was one of the earliest films shot in a documentary style (inspired by Nanook of the North) and because of how it was shot:
The basic story of The Viking is your classic “young man runs away and joins up with seal hunters to prove himself worthy of his girlfriend’s love”:
But other than the location aspects, and the seal hunting, why is The Viking interesting? After it premiered, the producer, Varick Frisell, decided “What this movie needs is more footage of ice floes.” So he and some film crew members went out to get pickup shots of the ice floes while their ship (the real ship named Viking) was hunting seals. The Viking (the ship) got stuck in the ice…
….and, on March 15, 1931, the good ship The Viking exploded, killing Frisell, his dog, and 26 other members of the crew.
As far as I know, and have been able to determine, this is the largest number of people killed in a single accident during the making of a film. I’m a little surprised I’d never heard this story before today.
TCM page on The Viking. Wikipedia. Entry on The Viking from the Canadian Film Encyclopedia.