By Andrea Shalal-Esa

Boeing spokesman John Williamson said the company received the notice from the Pentagon's Defense Contracts Management Agency (DCMA) on Friday, which means the government will not accept any aircraft manufactured at the plant until certain requirements are met.

Boeing produces its CH-47 Chinook helicopters and MH-47G Special Operations Chinook the at the plant, as well as the fuselages for the V-22 tilt-rotor aircraft that it builds with Textron Inc's Bell Helicopter unit.

"It's a serious matter and we are taking it very seriously," Williamson said, in response to a query about the government's action.

He said Boeing had halted production at the plant until the company was able to determine how the foreign object debris had gotten into the V-22 fuselage. He said the latest incident was discovered by Boeing during a quality inspection this week.

Williamson gave no details on what object had been found, but such cases often involve tools, stray pieces of wire or protective coatings that wind up where they should not be.

"The Level IV CAR (corrective action request) means that the government will not accept aircraft from this facility until we have satisfied their requirements," he said.

Williamson said Boeing workers at the plant were expected to report to work, despite the production halt. He said Boeing was working with the Pentagon to correct the problem, but it was unclear when the production line would be reopened.

He said an investigation was underway to determine if the latest incident involved any deliberate sabotage.

One individual was arrested and convicted of deliberately placing foreign objects in an H-47 helicopter in May, Williamson said.

Defense analyst Loren Thompson said the incident was troubling and raised questions about deliberate sabotage.

"There clearly is a pattern of foreign objects and material intruding into Boeing's rotorcraft process," said Thompson, chief operating officer of the Virginia-based Lexington Institute.

"I was actually in that plant a few months ago and, like other defense plants, it is extremely neat and clean, so these sorts of things don't usually happen by accident. You have to consider the possibility that someone is doing this deliberately."

(Editing by Andre Grenon)