Custard and rice pudding surprise

What caused the damage to this lorry? Custard, ma’am. Exploding custard plus some rice pudding, it’s reported. The truck was carrying 60,000 cans of custard and rice pudding when passers by warned the driver it was on fire. He leapt out of the cab just before the custard and rice pudding started exploding “like gunshots going off.” Luckily no-one was harmed.
I sometime play with custard because if you mix custard powder with a little milk or water, it creates an impact solid. When under pressure it acts as a solid, but as a liquid when no force is applied. You can pull it together quickly into a ball, throw it at a wall to shatter into pieces, each of which then forms a little pool of custard. I was told that if you fire a bullet into a drum of it, it will be stopped in four inches, and will then sink to the bottom.
However, I never thought of using it as an explosive. Wisely, I never use canned custard or rice pudding. You can’t be too careful…