A criminal investigation is under way after a video surfaced online showing a man urinating on a Kellogg's factory assembly line in the US, the company said.

The firm said it learned of the video on Friday and immediately informed law enforcement authorities and regulators.

A criminal investigation is being conducted by the US Food and Drug Administration's office of criminal investigation, the company said.

The graphic video shows a man urinating on an assembly line, then panning to a sign with the Kellogg's logo.

Kellogg's said its own investigation determined the video was recorded at its Memphis, Tennessee, factory in 2014.

"It is important to note that any products that could be potentially impacted would be very limited and past their expiration dates," the company said.

It said 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.

"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.

Kellogg's said it is still working to identify the individual in the video.