Jennifer Plank-Greer of Kokomo, Indiana, was visiting a home in Celina, Ohio, on May 6, 2012, when she started recording cellphone video of a man about to fire a rifle at a target in the backyard. Plank-Greer was 150 feet away as the man fired at his target, a refrigerator containing just 2 pounds of exploding targets, a product openly for sale at some of the country's biggest stores.

The refrigerator exploded, sending shrapnel flying in all directions. A metal fragment struck Plank-Greer's right hand, nearly severing it at the wrist. "In a blink of an eye ... it was gone," she said. She says she was unaware the refrigerator contained exploding targets.

Plank-Greer, who has since moved to Bradenton, Florida, because cold weather is painful for her injury, has undergone multiple surgeries to reattach her hand and attempt to restore some of its function.

H2Targets and Tannerite both make exploding targets whose key ingredient is ammonium nitrate, the same substance used in the Oklahoma City bombing that killed 168 people and injured more than 680 others in 1995 and in IEDs (improvised explosive devices) used against U.S. troops in Afghanistan. In 2013, the FBI issued an intelligence bulletin warning that exploding targets have "potential use as explosives in IEDs by criminals and extremists."

Yet today Tannerite can be legally purchased at most sporting goods stores. Gun enthusiasts buy it for target practice because it explodes when you shoot it, letting you know you've made the shot.

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TODAY national investigative correpsondent Jeff Rossen went shopping at one store and bought 40 pounds of it — enough to blow up a house — with no questions asked. And potential terrorists don't even have to show up at a store to buy Tannerite. A Rossen Reports producer bought the same amount, 40 pounds, online. A week later it was delivered to a doorstep in bulk.

Even some firearms experts call the situation unacceptable. "I'm a huge supporter of the Second Amendment," said Travis Bond. "But it's extremely dangerous, like a bomb for sale on the shelf."

Bond says that Tannerite is getting around the law on a technicality by separating the two ingredients in its explosive — ammonium nitrate and aluminum powder — even though the two are sold together.

"Everything you need comes with the package you purchase right off the shelf," Bond said. Though legal restrictions do not apply to the two ingredients when they are separate, he explained, "once it's mixed, it's classified as an explosive."

The Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) declined Rossen Reports' request for an interview, but Sen. Richard Blumenthal of Connecticut told Rossen, "This kind of bomb-making material is a real threat and a growing risk."

"You're a key member of the Judiciary Committee, which oversees the ATF," Rossen said. "The ATF doesn't classify this as an explosive. Why aren't you doing more?"

"There should be regulations that, in effect, either require licenses or better track who is buying these devices that are relatively new," Blumenthal replied.

Contacted for comment, Tannerite Sports LLC, makers of Tannerite, told NBC News: "No additional regulations are needed beyond current laws because the product is safe when used correctly," and "the only injuries that have ever happened were results from the shooter misusing the product." The company added: "Only girly-men want to regulate Tannerite Rifle Targets."

Rossen asked Blumenthal: "Will you talk to the ATF about changing the classification of this product?"

"I am going to press the ATF and other government agencies to do more and do it better," the senator replied.

The only state in the country that bans the purchase of exploding targets without an explosives license is Maryland. Everywhere else it's on the shelves right now.

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