While Guinness on their Facebook said this:
We can confirm that there was a small fire at the St. James’s Gate brewery site this morning. It has been contained. No-one was injured and there is no impact whatsoever on production. It occurred in a building that is seldom used.
Update: Original video pulled. Two alternatives:
Seems employees have been evacuated. No impact on production?
Update 2: view from Storehouse itself: