Two of the devices, one discovered late Tuesday and one early Wednesday, were mailed to former President Bill Clinton and Hillary Clinton’s residence in Chappaqua, New York, and the other to former President Barack Obama’s home in Washington, D.C.
The third device was discovered Wednesday morning in the mail room of the Time Warner Center building in New York City. CNN has offices in that building and was on the air when a fire alarm went off, alerting people in the building to get out.
Law enforcement authorities have described the devices as pipe bombs.
What is a pipe bomb and what can they do? Here's a look at the device.
What is a pipe bomb?
A pipe bomb is an improvised explosive device. It is made by putting explosive material in a tightly sealed section of pipe.
How does it work?
A pipe bomb does not need a high-level explosive to be lethal. A low-level explosive can cause tremendous damage.
A pipe bomb is just that, a bomb encased in pipe. Explosive material is put into a piece of pipe and the pipe is sealed at each end with steel or brass caps.
A fuse is inserted into the pipe – a lead wire to the fuse comes out through the capped end or through a hole that can be drilled into the side of the pipe. The fuse is usually connected to a timer or battery.
When the material detonates, the pressure causes the pipe to fragment, creating shrapnel.
How powerful can it be?
Because of its construction, it can be very powerful. The explosive material in a pipe bomb is under great pressure. A pipe bomb can also include other material such as nails and glass that would cause even more damage.