Explosion Investigation at Minnehaha Academy Likely to Be Complex

The investigation into the explosion at Minnehaha Academy Wednesday will be a complex one involving the state fire marshal, the Bureau of Alcohol, Tobacco, Firearms and the Minneapolis Fire Department.

And some experts tell 5 EYEWITNESS NEWS it could take months to sift through the rubble to figure out exactly where the blast occurred and why.

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Investigators may even go so far as to reconstruct portions of the blown out building – just like in plane crashes and other disasters.

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"For example, in the 35W bridge collapse, huge portions were removed and preserved," said Tim Fetterly, a Bloomington lawyer who specializes in building explosions and fires.

Fetterly has analyzed hundreds of cases in his 27 years and knows exactly what investigators are looking for.

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"They will be carefully analyzing the physical condition of the scene," he said. "What’s different? What’s unique? What caused this on this day?"

Natural gas explosions are triggered when gas escapes from pipes – the blast depends on how much gas and pressure are inside. The perfect mixture of gas and air – what scientists call the stoichiometric point – is the biggest level of an explosion.

RAW VIDEO: Minnehaha Academy Explosion

It’s potentially the most catastrophic, too.

"It’s a powerful substance," he said.

Fetterly adds that more often than not, investigators are not able to determine the ignition source.

It could be as simple as a light switch.

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