Construction at Oregon State’s Reser Stadium turned into an archaeological dig.

Crews digging in the Beavers’ north end zone Tuesday as part of an expansion project for OSU’s Valley Football Center unearthed a large femur bone, which anthropologists believe was from a mammoth. Bones of other extinct mammals were found at the site, too.

“There are quite a few bones, and dozens of pieces,” associate professor of anthropology Loren Davis said, according to an Oregon State press release. “Some of the bones are not in very good shape, but some are actually quite well preserved.”

The bones are are at least 10,000 years old, but more testing will need to be done to determine their exact age. And apparently, it’s not uncommon to find bones in the area of Oregon where Corvallis is located. Davis believes the end zone could have been a bog or a marsh at some point.

“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,” Davis said. “We had all of these types of animals in the Willamette Valley back then.”

Construction is set to be completed before the Beavers’ 2016 season, but it’s halted for now until all of the bones are dug up.

Thumbnail photo via Twitter/@oregonstateuniv