TORONTO -- One of Canada's largest chicken producers has launched an investigation into alleged animal rights violations at its slaughtering facility, a year after an Ontario court found it guilty of failing to provide humane treatment for thousands of poultry.

Maple Lodge Farms said it planned to probe allegations made by advocacy group Mercy for Animals Canada, which said it had obtained hidden camera footage from inside the company's plant in Brampton, Ont.

The group claims Maple Lodge Farms allows some birds to die of cold while being transported to the plant and subjects others to undue suffering before they're killed.

It also claims that such treatment persists despite Ontario court rulings that convicted the company of violating the Health of Animals Act and ordered it to spend at least $1 million over three years to ensure compliance with federal rules.

A spokeswoman for Maple Lodge Farms said word of these allegations has prompted the firm to take action.

"Although the documentation has not been shared with us, we find the written descriptions provided very disturbing," Carol Gardin said in an email to The Canadian Press.

"We have launched our own investigation and, in keeping with our zero tolerance policy for any violation of our animal welfare policies, we will take appropriate disciplinary action, including dismissal, in any instance where non-compliance is identified."

Mercy for Animals is basing its allegations on footage depicted in a video the groups says was shot in the months after the final court decision was handed down last March.

Voice-over on the video accuses the company of transporting chickens for slaughter in trucks that are not temperature controlled, allowing them to freeze in transit. Footage appears to show dead birds being unloaded at the plant.

The video further claims that surviving chickens are subjected to inhumane treatment upon arrival at the plant. It claims birds sustain broken bones and crushed heads after rough treatment, experience additional pain after being hung by one leg from a slaughter line, and are subjected to painful shocks when dragged through electrified pools of water that fail to knock them unconscious as designed.

Images from the video appear to depict birds with body parts trapped in cage doors, animals with protruding bones hanging in the plant, and chickens that emerge from the shock pool with their wing still flapping.

Mercy for Animals said these conditions were filmed despite a series of sanctions imposed on the poultry producer after the Canadian Food Inspection Agency laid charges under the Health of Animals Act. Court heard that more than 2,000 chickens died on two trips to slaughter in the winter of 2008-2009.

Evidence was that the birds succumbed after exposure to snow, frigid winds, and freezing temperatures during loading, transport, and unloading.

Maple Lodge Farms was convicted in September 2013 on two of the counts, and the company pleaded guilty to 18 additional charges last March.

In handing down her ruling, a judge ordered the company to spend at least $1 million over the next three years to modify its transport vehicles and make other changes to ensure humane treatment for the birds.

Gardin defended the company's practices, saying it follows standards considered the best in the industry and allows third parties to regularly vet its slaughter procedures.

"We work closely with government, academic and industry experts on a regular basis to review and enhance them," she said.