Here is a magnesium inoculation that went wrong.
They make a magnesium alloy that minimizes the reaction, such as nickle-mag4, or some other products.
Using raw magnesium is dangerous, and could burn a hole in the crucible or ladle.
This is not realy an explosion, but I think just a magnesium flare-up.
I have studied how to make ductile iron with nickle-mag4, and it uses a very special technique in a ladle.
I could make ductile iron, I just can't find anyone who will sell me nickle-mag4.
Note that these folks (I know them) are very well trained, and there is a situational awareness on the part of all involved.
There is no panic, just slowly moving into a position where folks get moved back into a safer position.
These folks have very extensive safety meetings, and plan every step before they light the furnace.