PHOENIX -- Forensic experts are examining evidence gathered from a package that was addressed to Maricopa County Sheriff Joe Arpaio and contained an explosive.
Investigators are expected to use the examination to try to determine the source of the materials used in the package discovered in a mailbox Thursday.
The package was intercepted after it had been left in a parcel locker in a rural part of Coconino County and was flagged by a mail carrier as suspicious.
Authorities used a water cannon to neutralize the package.
An Arpaio aide has said the package contained black powder and an ignition device, although he wasn't sure if it was packed into a container and would have exploded or simply ignited in a flash fire.
No arrests have been made.