CHARLESTON, W.Va. (AP) – The national Humane Society on Wednesday demanded Congress hold hearings on charges that poultry plant workers tortured birds before killing them, calling videotape of mistreatment at a West Virginia plant “undeniable and unmistakable.”

Pilgrim’s Pride, a supplier for KFC chicken restaurants, fired 11 workers at its Moorefield processing plant Wednesday, a day after People for the Ethical Treatment of Animals released video of workers kicking, stomping and throwing birds against walls.

Three of those fired were managers; eight were hourly employees.

“We will continue with this investigation until we’re confident that every employee – regardless of rank – who had knowledge of these incidents has been held accountable for their actions,” President and Chief Operating Officer O. B. Goolsby said Wednesday evening.

The Pittsburg, Texas-based company said it has put quality assurance monitors on both shifts at the Moorefield plant, and managers at the company’s 24 other North American plants have been ordered to educate workers about animal welfare policies.

Goolsby said Pilgrim’s Pride will ensure that all its factories “eliminate unnecessary harm and suffering.” The Humane Society earlier accused the company of allowing a callous attitude toward chickens to exist.

“The grotesque video of these activities is an indication of widespread mismanagement at this facility,” President Wayne Pacelle said. “Even if these were only the acts of a few individuals, one has to wonder where the supervisors were when this happened and why none of the other workers stepped in to stop this abuse.”

The Human Society also said the federal Humane Methods of Slaughter Act should be expanded to protect poultry from abuse.

A Pilgrim’s Pride spokesman, Ray Atkinson, said the company would cooperate with any government investigation.

PETA secretly shot film at the Moorefield plant between October and May, then released the images this week on the Internet as part of a campaign against KFC.

PETA spokesman Michael McGraw said the group wants all KFC suppliers to install cameras on slaughter lines that he said move too quickly and are staffed by poorly paid workers and uncaring managers. PETA also wants the phase-in of “controlled atmosphere killing,” in which chickens are gathered by machines instead of people.