The find made this year, considered to be “of great value”, came from a carving knife, Eduald Carbonell, one of the directors of the dig, said during a presentation of the discovery.
The site, near the northern city of Burgos, has been under excavation since 1978. In 2000 it was classed by UNESCO as a piece of world heritage.
The oldest parts of the site are one and a half million years old.
Stone tools discovered in this site confirm the continuity of human settlement in Europe, the researchers said.
Researchers have also found the remains of a large bear which is an ancestor to the brown bear that exists today.
Various remains of this species were found at the site, as well as those of other animals such as rhinos, giant deer, bison and wild donkeys.
During the current digging season at the site, which just wrapped up, archaeologists presented another rare item they discovered — a fossilized shoulder blade of a child between the ages of four and six dating back 800,000 years.
It was discovered in 2005, but since it was trapped in a block of calcified clay it took seven years of work to extract.