The breakfast cereal maker learned of the disturbing footage on Friday 11 March and "immediately" alerted law enforcement and US regulators. "We are outraged by this completely unacceptable situation, and we will work closely with authorities to prosecute to the full extent of the law," the company said in a statement.

According to its own internal investigation, Kellogg said the video was recorded at its Memphis, factory in Tennessee during 2014. The footage was posted online at the World Star Hip Hop site and appeared to show a man urinating on the assembly line, before moving shot to a sign with the Kellogg logo.

The company said the food items potentially affected "would be very limited and past their expiration dates" as the video was shot in two years ago. The products that were potentially impacted include Rice Krispies Treats, granola clusters used in some products and puffed rice treats that it no longer makes.

The US Food and Drug Administration's Office of Criminal Investigation said in a statement that it is aware of the video, according to an ABC News report. It said it does not confirm or deny investigations, but that "we can assure consumers that we take seriously our mission to protect the public health." Kellogg said it is still working to identify the individual in the video.

The footage was shot at a time when Kellogg and a union were involved in a bitter labour dispute, locking out staff. In November 2014, Kellogg announced Project K, a four-year programme aimed at reducing costs by about $450m (£314.6m) a year — partly due to demand for breakfast cereal decreasing as more consumers are eating while on their commute. In December 2014, the cereal company announced that it was closing its 90-year-old cereal factory in London, Ontario.

Betty Guyton, a 25-year employee of the Memphis plant, told the New York Times she was shocked by Kellogg's bargaining tactics because the company was previously considered a generous employer. "It feels like we have been absolutely violated," she said, adding that W.K. Kellogg, the company's founder, "would have been disgusted at what is going on here."

Kellogg also cut off the workers' health insurance as soon as the lockout began. It has kept the plant operating with replacement workers hired by a staffing agency.