SpaceX’s Falcon 9 rocket's stage booster toppled over and caught fire while landing on a droneship in the Atlantic Ocean after a launch from Florida early Wednesday.

Medical oxygen is also believed to have “played a significant role” in the fire’s rapid spread, according to the state fire marshal.

The Axiom-4 mission launch, the fourth private astronaut mission to the International Space Station, was canceled Tuesday night after SpaceX detected a liquid oxygen leak in its Falcon 9 rocket.

Medical oxygen is also believed to have “played a significant role” in the fire’s rapid spread, according to the state fire marshal. “Home oxygen was a known factor in about 20 fire deaths ...