An undercover video showing crippled and sick animals being shoved with forklifts has led to the largest beef recall in the United States and a scramble to find out if any of the meat is still destined for school children's lunches.

The U.S. Department of Agriculture on Sunday ordered the recall of 143 million pounds of beef from a Southern California slaughterhouse that is the subject of an animal-abuse investigation.

The recall will affect beef products dating to Feb. 1, 2006, that came from Chino-based Westland/Hallmark Meat Co., the federal agency said. The company provided meat to various federal programs.

Secretary of Agriculture Ed Schafer said his department has evidence that Westland did not routinely contact its veterinarian when cattle became non-ambulatory after passing inspection, violating health regulations.

"Because the cattle did not receive complete and proper inspection, Food Safety and Inspection Service has determined them to be unfit for human food and the company is conducting a recall," Schafer said in a statement.

A phone message left for Westland president Steve Mendell was not returned Sunday.

Agriculture officials said the massive recall surpasses a 1999 ban of 35 million pounds of ready-to-eat meats. No illnesses have been linked to the newly recalled meat, and officials said the health threat was likely small.

Officials estimate that about 37 million pounds of the recalled beef went to school programs, but they believe most of the meat probably has already been eaten.

"We don't know how much product is out there right now. We don't think there is a health hazard, but we do have to take this action," said Dr. Dick Raymond, USDA Undersecretary for Food Safety.

Federal officials suspended operations at Westland/Hallmark after an undercover video from the Humane Society of the United States surfaced showing crippled and sick animals being shoved with forklifts.

Two former employees were charged Friday. Five felony counts of animal cruelty and three misdemeanors were filed against a pen manager. Three misdemeanor counts — illegal movement of a non-ambulatory animal — were filed against an employee who worked under that manager. Both were fired.

Authorities said the video showed workers kicking, shocking and otherwise abusing "downer" animals that were apparently too sick or injured to walk into the slaughterhouse. Some animals had water forced down their throats, San Bernardino County prosecutor Michael Ramos said.

No charges have been filed against Westland, but an investigation by federal authorities continues.

About 150 school districts around the nation have stopped using ground beef from Hallmark Meat Packing Co., which is associated with Westland. Two fast-food chains, Jack-In-the-Box and In-N-Out, said they would not use beef from Westland/Hallmark.

Most of the beef was sent to distribution centers in bulk packages. The USDA said it will work with distributors to determine how much meat remains.

Federal regulations call for keeping downed cattle out of the food supply because they may pose a higher risk of contamination from E. coli, salmonella or mad cow disease since they typically wallow in feces and their immune systems are often weak.

Upon learning about the recall, some legislators criticized the USDA, saying the federal agency should conduct more thorough inspections to ensure tainted beef doesn't get to the public.

"Today marks the largest beef recall in U.S. history, and it involves the national school lunch program and other federal food and nutrition programs," said U.S. Sen. Tom Harkin, chairman of the Chairman of the Senate Committee on Agriculture, Nutrition and Forestry. "This begs the question: How much longer will we continue to test our luck with weak enforcement of federal food safety regulations?"

Advocacy groups also weighed in, noting the problems at Westland wouldn't have been revealed had it not been for animal right activists.

"On the one hand, I'm glad that the recall is taking place. On the other, it's somewhat disturbing, given that obviously much of this food has already been eaten," said Jean Halloran, director of food policy initiatives at Consumers Union. "It's really closing the barn door after the cows left."