PIPESTONE, Minn. – An undercover video shot at a Minnesota pork operation that supplies pork to Walmart prompted local law enforcement authorities in Pipestone, Minn., to launch an investigation, but no charges were filed in the case.

Mercy for Animals released the video which was taken at Rosewood Farms, a pig operation that is part of Pipestone Systems, a cooperative of family farms. A former employee who worked at the farm for 10 weeks reportedly shot the video and gave it to Mercy for Animals. The animal rights organization said the video shows "egregious animal cruelty".

Officials at Walmart said the retailer is conducting its own review of the video. In a statement, Pipestone System said it cooperated with the Pipestone County Sheriff's Office, and does not condone animal mistreatment.

"The complaint was lodged by Jessica Marie Buck, a former Pipestone System employee, who we believe to be an undercover activist with the Mercy for Animals organization," Pipestone System said. "It’s our understanding that the Pipestone County Prosecutor has determined not to bring any charges against any of the employees on the farm at this time.

"The Pipestone System immediately conducted an internal investigation of alleged mistreatment and discovered certain violations of its Animal Welfare Policy that resulted in the immediate termination of one employee, reassignment of another and follow-up training of the remaining employees," Pipestone System added. "The Pipestone System also requested and underwent an immediate third party external audit of the operations at this farm."

The Pipestone System noted that all its employees receive extensive animal welfare training, and workers are required to sign a pledge to immediately report any suspected abuse or mistreatment.

"Ms. Buck signed on to this pledge, specifically committing to report any animal welfare issues or concerns she witnessed. Unfortunately, no report of abuse or mistreatment from Ms. Buck was ever reported. Ms. Buck’s own actions while on the sow farm clearly violated our animal welfare policy."