This morning, I received information about a rash of "bottle bombings" taking place around the country, and thought I should pass along the warning to you.
The bombs are made of pop (or water) bottles that contain some Drano, water and tin foil. When the container is disturbed, a chemical reaction between the Drano and the tin foil creates high pressure within the bottle, resulting in an explosion. Apparently, these bottle bombs are being left in front yards and other locations where people are likely to discover the bottle, pick it up and move it. When that happens, the chemical mixture sets off the explosion after about 30 seconds.
There is a more thorough explanation about the way these devices are made, and a video clip of an explosion at http://www.snopes.com/crime/warnings/bottlebomb.asp
Even though these are just high-pressure explosions in plastic bottles, they are still dangerous and can cause serious injury, chemical burns, loss of eyesight, etc. If you find a suspicious object in your yard, the safest thing to do is to leave the object alone and call the police.