The Genius Media Nigeria reports that Videos on social media show money raining down as people scramble to pick up dollars strewn across the road.
It happened on the Interstate 5 in California’s San Diego county.
Police said the ensuing excitement saw drivers abandon their vehicles and block traffic. Arrests were made, with others who pocketed cash urged to hand it back.
One of the armoured vehicle’s doors popped open on the road, causing bags of cash to fall out and break apart at about 09:15 (17:15 GMT) local time.
“For whatever reason, money was falling out of an armoured car,” California Highway Patrol (CHP) Officer Jim Bettencourt said.
Video captured at the scene by fitness influencer Demi Bagby shows the road at a standstill, with passers-by grabbing and playing with littered $1 and $20 bills.
Two arrests were made at the scene, local media reported.
Highway police officials said the FBI were involved and urged people who grabbed cash to come forward.
Officer Bettencourt said anyone who stopped to pick up money could “possibly be facing charges”.
Curtis Martin, a sergeant with the CHP, said on Friday afternoon that about a dozen people had returned money they had grabbed to police.
“People are bringing in a lot,” he said, without giving a figure. “People got a lot of money.” (Text, excluding headline: BBC)