The United States Postal Service overpaid trucking contractors $61.5 million through its Voyager Card Program, which allows drivers to expense their gas on a credit card.

According to the inspector general, the Postal Service failed to identify fuel overpayments by contractors on Highway Contract Routes (HCR), which covers more than 17,000 drivers.

The Postal Service—which lost $1.9 billion in the second quarter of 2013, and owes nearly $50 billion in liabilities—has to collect millions each year from private individuals and firms contracted to deliver mail. These individuals are overcharging the agency for their fuel.

According to a report released last week, between 2009 and 2010 the Postal Service found $12.6 million in overpayments. That was $9.9 million short of the $22.5 million the inspector general identified.

The IG said time is running out for the Postal Service to recover the nearly $10 million it had not realized it lost.

"We are issuing this alert due to the urgency and time sensitivity associated with recovering any overpayments," the IG said. "The Postal Service’s ability to recover any overpayments for expired and non-renewed contracts becomes increasingly difficult as time passes."

"The U.S. Postal Service Office of Inspector General (OIG) has expressed continued concern with the Postal Service's control environment and related control weaknesses over the HCR Voyager Card Program," they said.

In addition, the Postal Service overpaid contractors $20.4 million between 2010 and 2011, and $18.6 million between 2011 and 2012, a total of $61.5 million since 2009.

It is not clear how much the Postal Service has recovered. An audit has not been conducted the Postal Service’s collection process, Agapi Doulaveris, a spokesperson for the OIG, told the Washington Free Beacon.

Doulaveris also could not say how many of the overpayments can be attributed to fraud, only that the fuel amounts surpassed what Postal Service contractors are allowed to spend on gas.

"These amounts relate to gallons purchased over the authorized contracted gallons for highway contracts," she said.

Contractors and Postal Service workers use Voyager Fleet Cards to pay for their fuel, repairs, and maintenance of their vehicles.

To combat abuse, the Postal Service instituted new rules for Voyager Fleet cards for Postal Service workers in 2011, including limiting transactions to three per day, not to exceed $300. They were also limited to spending $1,000 per month. The new rules did not apply to contractors, however.

"[T]eams con­tinue to find that managers are certifying reconciliations without proper receipts and that managers are not investigat­ing potential duplicate, incorrect, or fraudulent transactions," the USPS said, in its rationale for the guidelines.

In its response to the report, the Postal Service disputed the IG’s findings. However, the Postal Service admitted over 4 million gallons of gas were purchased improperly during each period.

Most recently in 2011 and 2012, contractors bought 4,687,032 gallons over their allotted amount, totaling $16,733,320.

A Postal Service spokesperson told the Free Beacon that the agency has recovered $43.3 million in overpayments they identified. That amount, however, is $18.2 million less than what the IG reported.

"The Postal Service disagrees with the method the OIG used to arrive at its figures," they said. "The Postal Service has recovered the overpayments identified during its reconciliation process."