Crews accidentally uncovered human bones believed to date back to the 1850s-'70s at San Francisco's Fort Mason compound this week.
Renovation crews were removing soil contaminated by lead paint from a historic building when they made the rare find on Monday.
The bones were just "a couple feet" underground, Picavet said. They were not neatly arranged and were in sort of a pile.
"It could be weeks if not months" before we get any clues about the identity of the bones or why they were there, Picavet said.
An archaeologist monitoring the renovation is now helping to document and catalog the discovery for research.
The bones could help people understand more about the use of Fort Mason and the medical practices of the time, Picavet said. There used to be a hospital at the former military installation.
To avoid looting, the exact location of the find is not being released.
In unrelated civil war news, two confederate drug-smuggling dolls were X-rayed Wednesday.
The examination confirmed the dolls had been used to smuggle medicine past Union blockades. Scientists said their heads were hollow and once contained quinine or morphine.