DIA spokesman Chuck Cannon told 9NEWS Friday that an audit over the summer revealed discrepancies between fees collected from taxi cab drivers, and what was actually deposited into the airport's bank account.

Cannon said cab drivers are required to pay a fee of $3.50 to the airport every time they go to from the holding lots to the terminal building to pick up a passenger. Instead of paying cash, the drivers buy tokens from vending machines. Cannon said staff from ground transportation empty the vending machines, and then deliver the cash to the airport's finance department.

"Every 2 or 3 days, two ground transportation employees go and empty those machines because they fill up with cash," Cannon said. "They put the money into deposit bags, locked deposit bags, and they take them up to the finance office to the cashier, and give them to the cashier, and get a receipt. And then the cashier or someone in the finance office takes over control of those bags of money and is supposed to deposit them into the Airport Revenue Fund, the bank account, the airport's bank account."

Cannon said the audit shows more than $100,000 is missing from that source of revenue. Auditors with the airport believe the cash disappeared over a period of the last two years.

"They did an audit of the deposits," Cannon said. "They reconciled the deposits with the receipts that the GT (ground transportation) people get every time they turn a bag of money over to the cashier. They get a receipt, and they reconcile these receipts with the bank deposits, and they discovered that they didn't match, that there was money that had been turned over to the cashier but had not been deposited."

Cannon said it's not clear whether the cash went missing in the hands of the ground transportation staff, or when the finance department handled the money. Cannon said, that's why this matter was handed over to Denver police. Detectives will determine exactly when and where the cash disappeared. Cannon said if there is a weakness in the airport's accounting system, the administration wants to get it fixed so this situation does not happen again.