Drivers jumped out of their cars to scavenge wads of cash after the doors of an armoured truck flew open while it was transporting money.
The extraordinary scene was caught on camera as the helpless truck driver resorted to filming those snatching the cash.
TikTok users also recorded themselves taking "free money" off the road and throwing it in the air, while cheering with excitement.
Police later arrived at the scene and arrested two people who locked themselves out of their car during the frenzy, the Daily Star reports.
The truck had been on the interstate motorway in Carlsbad in the US at around 9am when one of the doors reportedly popped open, spilling bags of cash into the road.
Fitness influencer Demi Bagby, who has 2.6 million followers online, filmed the incident on her phone.
"This is the most insane thing I've ever seen," she said.
"Someone dropped money all over the freeway - San Diego has shut down.
"Literally it has shut down, look at the freeway right now, oh my gosh."
Police confirmed that they have made two arrests in connection with the incident, with the California Highway Patrol saying that videos on social media show several people stopping to pick up the cash.
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CHP Sergeant Curtis Martin said: "There is a lot of video evidence of people picking up the cash, so we are going to be following up on every lead that we have.
"We did arrest two suspects on the scene.
"Those two suspects accidentally locked their car so it was blocking lanes of traffic, so they were still here when officers got here, so they're in custody."
The exact quantity of money that was dropped onto the highway is not clear at present, and a police investigation is ongoing.
Meanwhile, the San-Diego Union-Tribune reported that at least a dozen people had reportedly returned the cash they had picked up to the CHP.
