(ABC NEWS) -- A new security bulletin from the FBI showed the first image of one of
the shredded backpacks believed to have housed one of the explosive
devices in the Boston Marathon bombing Monday.
The unclassified bulletin was sent Tuesday evening to law enforcement
agencies across the country and said that the bomb inside the backpack
was an "improvised explosive device (IED)" made out of a common pressure
cooker. ABC News had previously reported that law enforcement recovered mangled parts of a pressure cooker bomb that included wires, shrapnel and a circuit board.
The advisory said there was "insufficient evidence" to determine if
the second explosive, which was also hidden in a backpack less than a
block away, was made from a pressure cooker as well.
Authorities have not yet determined the fusing system for the devices
or what exactly set them off, the advisory said. The blasts erupted at
approximately 2:50 p.m. EST near the marathon's finish line Monday
afternoon killing three people - including an 8-year-old boy - and
injuring more than 170 others. Authorities have no suspects in the case
and no group, domestic or international, has taken responsibility for