Several people were able to gather money that somehow fell out of an armored vehicle on De La Cruz Boulevard, at the border of San Jose and Santa Clara.
Witnesses said the armored vehicle attracted attention when they saw money fluttering through the air and a guard trying to retrieve the cash.
"The guy's hands were too full and the wind was just blowing," San Jose-resident Ernie Mendez said.
Mendez said he saw "wads, stacks" of bills blowing about. "It looked like millions of dollars, you know what I mean."
GardaWorld, which operates the armored vehicle, said it is conducting an investigation into the incident and could not disclose any additional details.
Police said GardaWorld did not report the incident or the lost cash.
While a man told NBC Bay Area he retrieved $40, police point out it is not free money if you know where it came from.
"Whether it fell out of an armored truck or if you saw someone drop a wallet, then you are liable to return that money either to that person or the police department," San Jose Police Sgt. Heather Randol said. If not, then you are committing theft."