That's prompting fears of millennial destruction.
"We have a great concern, and we're not going to hide that concern," said Fresno Police Chief Ed Winchester. The Fresno police force is in charge of the bunker as the agency leading a bomb squad that serves Fresno, Madera, Mariposa and Kings counties.
The explosives - 125 pounds of dynamite and the military explosive C4, plus 75 pounds of gunpowder - were stolen between Saturday and Monday from a concrete bunker about 20 miles northeast of Fresno.
"If you're an engineer, you can take down a high-rise with that. But if you put it all in a box and set it next to a wall, it wouldn't do much other than to destroy some of that wall," said police Lt. Andy Hall.
Blasting caps needed to detonate the explosives were left behind.
The burglary's timing heightened fears of New Year's Eve attacks.
"We're looking at increasing security for New Year's, and we're reassessing our deployment in light of this," Winchester said. "We are taking a look at potential targets within our city."
Fresno Mayor Jim Patterson said the city's millennium celebrations will not be canceled.
No suspects had been identified Tuesday evening. The Fresno County Sheriff's Department, Fresno Police Department, Clovis Police Department and the Bureau of Alcohol, Tobacco and Firearms are jointly investigating.
Mark Loizeaux, president of Controlled Demolition Inc. in Maryland, said the danger was minimal.
"The people don't know what they were doing, or they certainly would have taken the detonators. It sounds like a childish prank," said Loizeaux, whose company has demolished more than 1,200 buildings. "The gasoline in your gas tank is technically more dangerous than this product, because you can set it off with a match."
The bunker, is half-embedded in a hill, about 8 feet wide, 12 feet long, and 10 feet high. It is made of reinforced concrete. Its door is heavy steel with several locks. The bunker is also isolated by a locked gate and a chain link fence toped with barbed wire.
The bomb squad uses the explosives to destroy ammunition, bombs and explosives confiscated by local law enforcement.
On Nov. 14, suspects stole about 100 pounds of stick dynamite from a lumber company's storage facility in Standard, said Tuolumne County Sheriff's Sgt. Allen Dahl. No one has been arrested.
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