A bomb squad has destroyed hand grenades and other explosive materials found in an old backpack beneath a highway bridge outside Los Angeles, according to news reports.

The Orange County Register reports that six grenades, several blasting caps and black powder were found inside the deteriorating backpack, which may have been deliberately left months ago under the bridge in an industrial area of Anaheim. Several businesses were evacuated.

Jim Amormino, spokesman for the Orange County Sheriff's Department, said other types of ordnance were found under the bag and partially buried nearby. He said the explosives could have caused major structural damage.

Whoever left the bag "had some type of knowledge of explosive devices," said Amormino, noting that some of the grenades apparently had once been inert but were later filled with black powder.

County crews working in a drainage ditch near Lakeview and Orangethorpe avenues found the backpack. Tracks carrying freight and passengers trains are not far away, officials said.

The FBI has joined the investigation.

USA Today