PHOENIX -- Inspectors found more than $1.2 million in cash hidden in the spare tire of a commercial tractor-trailer on Monday, the Arizona Department of Agriculture said.

Officials said the big rig pulled into the Sanders Port of Entry on Interstate 40 around 6:45 a.m. Because the truck was hauling produce, it required an ADA inspection.

Plant Services inspectors examined the load of watermelons and onions and said they became suspicious when they noticed rotting produce. Officials said the driver gave the inspectors inconsistent explanations of the shipment's origin.

The inspectors said their attention was also caught by a brand new spare tire secured underneath the trailer with an unusually large padlock.

When a check of the driver's information through the Motor Vehicle Division revealed that his insurance was expired, the inspectors called the Department of Public Safety, officials said.

DPS officers searched the big rig and found $10,000 in cash in the passenger cab, according to ADA.

The inspectors then urged the officers to examine the spare tire. Officials said the officers pried it open, revealing $1,220,385 in cash inside.

The driver and his passengers were taken into DPS custody, interviewed and released. Officials said further investigation will determine whether the three will face any charges.

The tractor-trailer was seized and the produce destroyed because it was rotting.

Officials said the initial stages of their investigation indicated that the money stemmed from some sort of illegal activity and that the tractor-trailer had been headed back to the criminal organization.