Washington (CNN) For the second time in two months, the US Air Force has stopped accepting deliveries of new Boeing KC-46 tanker and refueling aircraft after debris was again found in some of the planes coming off the production line.

"We actually stopped again the acceptance of the KC-46s because of foreign object debris that we found in some closed compartments," Air Force Secretary Heather Wilson told Congress Tuesday.

"We've got corrective action in place, including (inspections) in some of those closed compartments to make sure that the production line is being run the way that it needs to be run," she said.

The issue remains a quality control failure and "unrelated to design or engineering specifications," according to Ann Stefanek, an Air Force spokeswoman.

CNN reported last month that the Air Force first halted deliveries on February 20 after trash and industrial tools — known as foreign object debris, or FOD — were found on board some planes after production was completed.

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