Law enforcement and fire department volunteers have responded to several calls since Christmas to reports of loud explosions.
White County Fire Department spokeswoman Ana Newberry said "They (the targets) are a binary explosive that is composed of two chemical compounds, Ammonium Nitrate and Flash Aluminum. The Ammonium Nitrate what provides the explosive charge power. The Flash Aluminum is known as a sensitizer, it is what allows the Ammonium Nitrate to combust."
Newberry says the devices are completely legal and can be purchased locally.
http://accesswdun.com/article/2011/12/244622