IIRC, the gas utility has said it wasn’t a gas leak.
“The cause of the explosion is still a mystery, 18 hours later. Authorities said they don’t have an idea of what caused it, but are not ruling anything out.
City officials estimated damage at $3.5 million. A local gas utility said an initial inspection found no gas leaks in the area.”
From the article:
Dan Considine, a spokesman for Citizens Energy, said the utility had not received any calls from people smelling natural gas in that area.
"Most of the time, when there's a gas leak, people smell it," he said. "But not always."
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Stating no gas leak was reported, is not the same as saying it was not a gas leak. I would bet money on a gas leak.