The frenzy happened during morning rush hour in East Rutherford.
Videos shared online show people stepping out their vehicles and walking through traffic, trying to collect money amid cars and trucks.
"People went a little bit crazy when they saw the money," said Danielle Shah, 29, of Bloomfield, New Jersey, who witnessed the incident from a bus she was riding into New York.
"I mean, it seemed like the people who got out of the car – they just didn't care. They parked their cars in the middle of the highway."
A Brinks truck idled in the right shoulder with its lights flashing as the bills blew around the highway. One video showed the bashed-in front end of a sedan as traffic crawled through the blizzard of bills.
Brinks is a provider of armoured transportation.
Police said the chaos led to two crashes, though it's unclear whether anyone was injured.
It appeared that the armoured vehicle had an issue with the lock on one of its doors, Police Captain Phil Taormina said.
In a statement, Brinks confirmed the truck belonged to the company and said an investigation is under way, but declined further comment.
Police said they don't know how much money spilled.
Authorities told 6ABC they received a call about an armoured truck spilling cash on the western lanes of the highway.
Police tweeted that anyone with information or video should contact them.
These kinds of spills have happened before.
In May, a Brinks truck spilled hundreds of thousands of dollars on an Indianapolis interstate when its back doors swung open. A similar incident unfolded in Maryland in 2012. About $6,000 spilled out then.
AP contributed to this report.
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