Willard
This comment is interesting from the same page as the photos of the damage.
"Iran was apparently performing a volatile procedure involving a missile engine at the site when the blast occurred."
Along the lines of
"Messy safety procedures and / or trying to do some things too fast
and cutting corners, causing fatal safety mistakes"
Re the "then either the launch pad was reasonably close to the buildings"
I would be surprised if they made that mistake. Having been to Woomera Rocket range, the closest building to the launch sites was quite some distance away, far enough not to be affected by an explosion on the launch pad.