The bombs appeared to have been built by packing the pressure cookers with a black powder explosive as well as nails and pellets to maximize casualties, a lawmaker briefed by investigators said.
In the past, the U.S. government has warned federal agencies that terrorists could turn pressure cookers into bombs by packing them with explosives and shrapnel, and detonating them with blasting caps.
The U.S. government has warned federal agencies in the past that terrorists could turn pressure cookers into bombs by packing them with explosives and shrapnel and detonating them with blasting caps.