An anti-tank rocket launcher and explosives were discovered off the Golden State Freeway near Newhall on Tuesday by California Highway Patrol officers, authorities said.
The cache, which also included a rocket, a hand grenade and 1 pounds of plastic explosives, was later found to be inoperable, a Los Angeles County sheriff's spokesman said.
Sheriff's Department explosives experts took the explosives and weapons to the Peter J. Pitchess Honor Rancho in Saugus, where they were studied. The standard American military-issue rocket and hand grenade lacked explosive charges, and the plastic explosives did not have fuses, the spokesman said.
The CHP officers, in the area investigating an auto theft, found the cache about 10:30 a.m. in a wash alongside the freeway near The Old Road, authorities said.
But a CHP spokesman said details of the discovery could not be released because they are "sensitive to the investigation."