LOS ANGELES — Police are investigating poultry producer Foster Farms after an animal-rights group shot undercover video showing some chickens being slammed upside-down into metal shackles, punched and having their feathers pulled out while they were still alive.

The video, which will be released today, was shot by the Los Angeles-based Mercy for Animals, which advocates against eating meat. The group said the footage was shot between April and June at a Foster Farms slaughterhouse in Fresno and the company’s nearby farms.

Tony Botti, a spokesman for the Fresno County Sheriff’s Office, said the agency is investigating the allegations after receiving a complaint from Mercy for Animals.

Foster Farms spokesman Michael Fineman said in a statement that the company has launched its own investigation and will fully cooperate with authorities.

“The behavior of the individuals in this video is inappropriate and counter to our stringent animal welfare standards, procedures and policies,” Fineman said. “We believe raising chickens humanely is simply the right thing to do, and we take our commitment to humane values very seriously.”