Company's planned explosion of old mortars startles NW metro neighbors

A loud explosion heard Tuesday afternoon in the northwest Twin Cities suburbs was the planned demolition of old U.S. Army mortars.

Orbital ATK detonated the explosives from several mortars simultaneously at its 3,000-acre weapons test facility near Elk River, said Jarrod Krull, a spokesman for the company's armament systems division.

"Those weapons systems contained some high explosives," he said. "And so when we were going about our demilitarization process, those weapons made a bigger boom than what our neighbors are used to hearing."

The blast could be heard for miles.

Krull said the explosives were detonated remotely, and no one was injured. But he says neighbors shouldn't expect too many more huge explosions.

"That's not going to be the norm going forward. It'll be back to more of the things they're used to hearing — guns firing, and maybe a little bit smaller detonations."

Krull said contrary to social media posts, the explosion was not accidental.