A mammoth discovery has been made underneath a US university's football stadium during construction work.
Unbeknownst to Orgeon State University, their Reser Stadium grounds were built on top of a graveyard of ancient and extinct animals including what is believed to be a mammoth.
Work to dig up the north-end zone as part of the Valley Football Centre expansion and renovation project was immediately stopped following the find of a large femur and bones from other animals in varying degrees of preservation.
Associate professor of anthropology at the university Loren Davis says there doesn't appear to be any signs of human bones or artefacts and more testing will be needed to figure out how old the bones are.
The find isn't unusual given the Willamette Valley, near the university, is a known area where animals, including mammoth, bison and "some kind of camel or horse", had previously been found in a 3-metre deep plot in an area which could have been a bog or marsh.
"Animals who were sick would often go to a body of water and die there, so it's not unusual to find a group of bones like this," assoc prof Davis says.
A digger driver was the first to come across the femur and told university officials.
While worked stopped in that area, the construction crews have moved to another site to continue their work causing minimal disruption.
Assoc prof Davis says the animals don't appear to have been killed and there isn't any evidence of humans at the site.
Because of that, the site isn't considered part of an archaeological site.
However, assoc prof Davis says it is nonetheless an important find and will provide valuable information.
The bones will be soaked in water to prevent further deterioration and will hopefully be sent for carbon-dating to discover how old the animal is.