Boeing’s troubled KC-46 tanker deliveries to the U.S. Air Force have been suspended as the service investigates a series of problems with foreign object debris, its top acquisition official confirmed Friday.

Will Roper, the service’s assistant secretary for acquisition, technology and logistics, told reporters that it will likely be “some time” before the service begins accepting new tankers from Boeing. “I was able to get some data from our team on the foreign object debris that’s being experienced on the KC-46 line. It’s still to be determined how extensive and how far into the production line it goes,” he said.

During a Thursday afternoon roundtable with reporters, Roper said that the Air Force had grounded planes for about a week due to concerns about tools and other foreign object debris left in the aircraft — a potential safety hazard. The issue was first reported by The Seattle Times.