http://news.yahoo.com/deadly-blast-devastates-indianapolis-neighborhood-220044324.html I could see an explosion taking out a few homes around the epicenter, but what could devastate an entire neighborhood like that? I guess they were fortunate only two people were killed...
Black ops. Preformed by a government agency which does not exist targeting a national security threat you don't need to know about.
These days, its just likely home made bombs. The question is it of the Al Qaeda or Stormfront variety.
It's looking more and more like a gas leak/faulty furnace: http://www.cbsnews.com/8301-201_162-57548442/owner-of-exploded-ind-home-cites-faulty-furnace/
Police have opened a homicide investigation. http://www.wthr.com/story/20140143/indianapolis-explosion-investigated-as-criminal-homicide As flow predicted, Walter White seen fleeing the area. Police are on a lookout for a white work van and are offering a reward to anyone who can identify it leading to an arrest of the occupants.