To protect his identity and frustrate possible retaliation, the undercover investigator behind the biggest beef recall in U.S. history refuses to disclose his name, his marital status, his hometown, his job background or even his age. One of the few personal things he will reveal is his culinary preference: He's a vegan.

But in a telephone interview Monday, the investigator for the Humane Society of the United States sketched a vivid, bleak account of his six weeks at a Chino slaughterhouse that supplied meat to school lunch programs and supermarkets throughout the U.S.

By day, the investigator said, he helped drive cattle from trucks and pens into a chute that led to the killing floor. But at the same time, he employed a tiny, hidden camera to film the alleged brutalization of animals too weak or sick to walk to slaughter. Under federal regulations, only animals able to walk on their own can be used for meat.

At night, the agent said, he retired, exhausted and manure-flecked, to an Ontario motel to chronicle his findings in a notebook and lock his videotapes in a closet safe.

"It was so blatant, so commonplace," he said, speaking from a location he wouldn't reveal. "It was so in-your-face . . . they were pushing animals we felt never should have qualified for human consumption."

The video produced by the undercover operation led the San Bernardino County district attorney to file criminal charges against two workers at Hallmark/Westland Meat Packing Co. and prompted the U.S. Department of Agriculture to announce the recall of 143 million pounds of beef. USDA officials said they believed most of the meat had already been consumed, and that the risk to the public was minimal.

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