I looked quite closely at the vids. What I saw was the main fire in the center of the screen, with smoke trailing off to the left. What came in from the left was obviously not a missile, but rather the leading edge of the big explosion that happened off screen to the left.
For you conspiracy theorists, you should take a look at some of the before, during and after stills. You'll see that the "big" explosion did not occur at the site of the fire, but rather way off to the left where the main storage facility was that held all the fertilizer that exploded. Probably ignited by flying sparks, etc.