A truckload of missing ballots - more than 60,000 of them - were found Tuesday after a week of going unaccounted for. What we found is an increasingly nasty back-and-forth between the Postal Service and the Adams County Clerk over who is to blame.

KUSA — The 61,000 voters in Adams County who've been waiting on ballots in the mail are waiting no more: the post office said they've been delivered. Though it’s still unclear who should be held accountable for them going missing in the first place.

State and local election officials traded blame with the United States Postal Service on Wednesday as they investigated how an entire truckload of ballots went unaccounted for between Oct. 15 and Oct. 22.

Fifteen XPO Shipping trucks, all carrying ballots printed by K&H Printing near Seattle, arrived at the USPS general mailing facility in Commerce City on Oct. 15. The ballots were set to be delivered to four counties in Colorado, with four full trucks worth of ballots designated for Adams County.

USPS staff accepted the parcels from all but one truck. USPS Colorado spokesperson David Rupert told 9NEWS that the driver lacked sufficient payment documentation that USPS needs to accept the delivery, adding the facility needs to keep track of thousands of pieces of mail per day.

An executive with K&H and Republican Adams County Clerk and Recorder Stan Martin, who is running for reelection in November, told 9NEWS that the USPS employee should have reported a rejected truck to a facility supervisor.

Martin, as well as Colorado Deputy Secretary of State Suzanne Staiert, said Wednesday that USPS staff should have known that shipment contained ballots based on packing, and that they have an agreement with USPS to always accept ballots in their facility.

“You know, I’m frustrated,” Martin said. “You know the USPS has a responsibility that when they reject ballots, that they have a responsibly to notify my office, and certainly if they’re not going to notify my office, then they have a responsibility to notify the secretary of state’s office. That didn’t happen in this case. I talked to them this morning, their protocol is they don’t reject ballots … They had information that this truck with our 60,000 ballots on that truck was rejected, and they sat on that information for a week.”

According to Martin and K&H, the XPO driver went to his company’s lot in Henderson, Colo. after leaving USPS. The driver left the truck there, but according to Martin, that driver failed to report that to his own supervisor, as well.

"There is certainly blame on both sides, the post office and this subcontractor who made the delivery. We don’t blame him for leaving the lot. He didn’t have any choice to leave the lot when his stock got rejected, but once he got back to the lot where he locked it up, he had an obligation at that point, we believe, to inform the contractor, to inform the county and for someone to inform the secretary of state’s office," said Staiert.

Rupert told 9NEWS over the phone that he knows of no agreement requiring automatic acceptance of a large shipment of ballots.

"The 'no ballots will be rejected' is in regards to completed ballots. It's our assurance that every ballot deposited by the voter into the mail stream will be delivered promptly to the individual county clerk and recorder," Rupert followed up in an email. "All ballots going to the voter need to the have the proper postage paid. We are governed by federal regulations which have certain documentation and payment processes that both us and mailers follow."

He said that the issue wasn't "insufficient payment," but rather a documentation issue regarding payment.

Rupert said that a request for an investigation will be submitted to the U.S. Postal Inspection Service and the Office of Inspector General.

Staiert assured 9NEWS this case has nothing to do with voter fraud.

“It’s a series of mistakes, and anybody at any point had they notified the county or the secretary’s office this could have been taken care of days ago,” she said.