The US Department of Agriculture shut down a slaughterhouse in California's central agricultural heartland because of a graphic video showing cows being mistreated during the slaughtering process, officials and activists said.
The agency's Food Safety and Inspection Service said in a statement that it was conducting an investigation and that inhumane treatment of animals was unacceptable.
"Upon confirming several humane handling violations, (the Food Safety and Inspection Service) suspended operations at the facility and is prepared to take further action as warranted by the investigation," the statement said.
The plant was shut down on Sunday, the USDA said, and several teams of investigators were sent to California.
Video of the facility posted online by activist group Compassion Over Killing, shows cows at the Central Valley Meat Company flailing wildly as they are dragged by one leg on a conveyor belt on their way to be slaughtered.
Video shows other lame, sick former dairy cows being shot in the head multiple times and struggling before they die. In one portion of the video, a worker stands on a cow's nostrils to kill it after the cow is shot in the head.
The video also shows cows that appear to have difficulty standing being electrically prodded to walk on their way to slaughter. The USDA does not allow cows that cannot stand on their own to enter the food supply.
The USDA said in a statement after activists posted the video online that footage provided to them did not show a "downer" cow entering the food supply, but added they would investigate food safety as well as humane treatment issues.
The farm, based 30 miles south of Fresno in rural Hanford, supplies meat to the National School Lunch Program, according to the activist group.
California-based fast-food chain In-N-Out Burger immediately suspended its relationship with the farm after hearing of the investigation, the company's chief operating officer, Mark Taylor, said in a statement.
"Central Valley Meat was one of several companies that supplied the beef chucks we use to make our hamburger patties," he said. "As soon as we became aware of the allegations regarding Central Valley Meat Company and their handling of cattle, we immediately severed our supplier relationship with them."
Central Valley Meat Company said in a statement emailed to Reuters that it was "extremely disturbed" to find it was suspended because of a third-party video, but noted it would co-operate fully with the USDA investigation.
"We take these allegations seriously and we are committed to correcting any problems identified on the video as quickly as we can," the company said, adding that it had retained an outside animal welfare expert to conduct an internal investigation.
An undercover activist shot the video at the farm in June and July, the animal rights group said.
In 2008, the Humane Society of the United States captured employees of a California meatpacking plant in Chino torturing cattle and processing the unfit animals for human consumption in a gruesome undercover videotape.
That video's release led to the record recall of nearly 65 million kilograms of meat by the Hallmark/Westland Meat Packing Company.