Product Used in NYC Bomb Can Be Purchased Online Tannerite residue found in bomb, official says By Evann Gastaldo, Newser Staff Posted Sep 19, 2016 6:04 PM CDT 47 comments Comments In this Saturday, Sept. 17, 2016 frame from video provided by Orangetheory Fitness Chelsea, a door shatters after an explosion in the Chelsea neighborhood of New York. Investigators scrambled Sunday to find out who planted a bomb that rocked Chelsea, scouring shrapnel, forensic traces and surveillance... (Orangetheory Fitness Chelsea via AP)In this Saturday, Sept. 17, 2016 frame from video provided by Orangetheory Fitness Chelsea, a door shatters after an explosion in the Chelsea neighborhood of New York. Investigators scrambled Sunday to... (Orangetheory Fitness Chelsea via AP) (Newser) – A legal product that can be purchased online or at a sporting goods store was used in the bomb that went off in Manhattan Saturday, USA Today reports. Tannerite is a product typically used for target practice; it is placed on targets and explodes when struck by a bullet from a high-powered rifle. It's sold in two inert parts (ammonium nitrate and aluminum powder), neither of which is regulated by the ATF. Once those two parts are mixed together, it only explodes if a bullet hits it and is considered very stable, a corporate investigator for Tannerite says. Tannerite residue was found inside the bomb that exploded in Chelsea, a federal law enforcement official tells USA Today. A post on the company's Facebook page Monday reads, "The entire staff of Tannerite stands together in the abhorrence and unintended use of all products that are misused for violence and hate." It goes on to note that its investigator is working to verify that Tannerite was indeed used in the bomb. A former FBI agent tells CBS News Tannerite appears to be "on the defensive." "It’s just something we have to be aware of that these terrorists are very clever at finding out what components can come together and make an improvised exploding device," he says. Forbes has more on the science behind Tannerite.