By the time officers arrived Thursday morning, those who had grabbed the cash were gone.
A statement from police spokesman Jim Sughrue said a Loomis armored car was on the road when the back door unexpectedly opened as an employee in the truck was trying to better secure the door.
The police statement said a brick of money fell out and scattered $20 bills when it hit the road. Police did not say how much money was in the brick.
Police reported no wrecks or injuries in the cash grab or cleanup.
Police say some people have returned some of the $20 bills.