(CBS) – An explosion Monday afternoon in southwest suburban Joliet leveled a residence, but no one was home at the time of the blast, authorities said.

The explosion occurred around 2 p.m. in the 700 block of Lambeth Lane and developed into a raging fire. The fire was nearly out by 4 p.m., and the explosion’s cause was unknown.

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A home is engulfed in flames after an explosion in Joliet. (Marge Brennan)

A home is engulfed in flames after an explosion in Joliet. (Marge Brennan)

Neighbor Marge Brennan said the boom “was the loudest things I’ve ever heard.”

Then it hit her: Was the little neighbor boy, Niko DeMichael, home when the house exploded?

That same thought occurred to Niko’s older brother, Matt DeMichael, as he came off the bus and saw his home in flames.

“I didn’t want to have the thought in my mind that he might not be alive,” Matt told CBS 2’s Brad Edwards.

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It turns out his little brother wasn’t home yet; he arrived just after it went up.

Father Nick DeMichael says: “I almost had a heart attack when I heard it, because Niko would have been home, and an hour after that Matt would have been.”

He adds: “There is a God out there, because if there wasn’t this would have been a lot worse.”

Officials said all signs point to a gas explosion. Nicor was called to the scene.

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Smoke billows from a house-explosion scene in Joliet (Marge Brennan).

Smoke billows from a house-explosion scene in Joliet (Marge Brennan).