I received a caution in the mail and, unfortunately, it checks out as true. I have reworded it here and provided a handling that was not in the original post.
Be cautious when picking up sealed, empty containers, specifically discarded plastic or glass bottles.
Miscreants are putting Drano (a substance that unblocks drains), tin foil and a little water in plastic drink bottles and capping it up – leaving it on lawns, in mail boxes, in gardens, on driveways etc. just waiting for you to pick it up intending to put it in the rubbish.
If the bottle is picked up and shaken even just a little – in about 30 seconds or less it builds up enough gas to explodes the bottle with sufficient force to cause harm. The liquid that comes out is boiling hot as well.
Now what the alarmist who wrote this does not mention is that these bottle bombs can be instantly defused by unscrewing the cap slightly to prevent a pressure build up. Of course they still need to be handled with care so you do not spill the contents over yourself. http://www.hoax-slayer.com/drano-bottle-bomb.shtml