But he said it did not contain nails or metal that would have served as deadly shrapnel, as in some past bombings.
Devices in all three bombings contained nails.
But officials confirmed earlier that the devices used in the winter bombings, like the Olympics bomb, contained nails and other shrapnel.
The bombs contained longer and better-packed nails to increase deaths and injuries, a senior officer said.
The bombs, which were strapped to the waists of the bombers, contained nails and metal shards.
Other officials said the bombs contained nails and that the packages containing the bombs may have been mailed from the same location.
The bomb contained nails about 7 or 8 inches long, Sergeant Mosier said.
Over on the workbench was a large plastic tray containing assorted nails.
Do not burn wood containing nails, screws or other metal hardware.
Initially the cause of the explosion was unclear, but was found to have been a bomb containing nails and ball bearings.