Archaeologists excavating a housing development found a prehistoric milling site estimated to be 8,000 years old, officials said.
Large arrowheads, hearths and stone slabs used to grind seeds and acorns were among the items found at the site at the base of the Angeles National Forest, according to archaeologists from Cogstone Resource Management Inc.
No human or animal bones were discovered, the company said.
The consulting firm was hired by Azusa Land Partners, which is developing 1,250 homes on the 520-acre site. Workers removed and cataloged about 100 tools and implements used by the Gabrielino-Tongva tribe, which lived in the area before Europeans arrived, said Cogstone President Sherri Gust.
Archaeologists have known since the 1960s that the area contained artifacts, but the exact location of the milling site was not discovered until three weeks ago, Gust said.
Azusa is about 30 miles east of Los Angeles.