Massive House Explosion in Indiana; What Caused the Big Blast?

A ferocious explosion in the night, home after home leveled into cinders and rubble. Tonight, investigators are pouring over the clues to find the cause and to alert other neighborhoods across the... See More

A ferocious explosion in the night, home after home leveled into cinders and rubble. Tonight, investigators are pouring over the clues to find the cause and to alert other neighborhoods across the country. Abc's john slefchriffen has more. Reporter: The explosion was so intense, now it looks like a tornado tore through this indianapolis community. For dozens of families, the cruel reality of saturday night's blast is just starting to set in. All of a sudden, the house shook, things fell. We ran outside and we just see the whole house, I mean, itas like, four, five houses down from us and it was in flames. Reporter: Federal authorities are now teaming up with local agencies to figure out how this happened. We're looking at everything. All causes, all possibilities. Reporter: Authorities say at thoint, nothing has been ruled out. Yet the mayor of indianapolis says it was not caused by a bomb or an exploding methamphetamine lab. Law enforcement sources tell abcnews the leading theory, that it was caused by a gas explosion. It's too early to speculate. Reporter: Investigators believe it could take weeks before they know what triggered the mysterious blast that caused so much damage. John schriffen, abc news, indianapolis.