It probably was a gas leak.
It just seems to be taking a while to reach that conclusion at the scene.
Normally, I’d expect there to be gas leaks after the explosion, even if there weren’t any before, since some pipes are blown apart now, and fittings are gone, etc. At least until the utility crews can turn off the gas further back down the line.
If you didn’t smell gas before, I’d expect you to smell it shortly after.
As I said earlier, there was a tiny gas leak in a fairly large building where I work, and the smell was obvious. There was no doubt we had a gas leak, the only question was where it was coming from, and a sniffer found the source pretty easily.
The Gas utility shortly after the explosion shut off gas to the area, eliminating gas to 30 homes, IIRC. They inspected the gas lines outside the perimeter of the home that exploded and found no leaks.
Inside the home, as you said, there would be lots of leaks now as the gas pipe and fittings are scattered over a large area.
The home was not occupied at the time and had been unoccupied for a little while, where gas could accumulate inside with little chance to notice.
There is a claim the house had problems with the gas heat the week prior to the explosion.
http://www.freerepublic.com/focus/f-news/2958364/posts?page=39#39
Many distribution systems have valves which shut off if there is a sudden flow increase/pressure drop in the line. If that shutoff works, there shouldn't be any more major leaks and a very limited amount of gas coming out of the line