Boeing Co. said on Thursday a supplier told the plane-maker that certain 787 Dreamliner parts were improperly manufactured, the latest in a series of problems to plague the wide-body aircraft.

The company did not name the supplier, nor did it identify the part, although the Wall Street Journal earlier reported that the defect involved certain titanium parts that are weaker than they should be.

"While our investigation is ongoing, we have determined that this does not present an immediate safety of flight concern for the active in-service fleet," a company spokeswoman wrote in an emailed statement.

Undelivered aircraft would be reworked as needed, Boeing said, adding that any fleet actions would be determined through its normal review process and confirmed with the U.S. Federal Aviation Administration.

The FAA did not immediately respond to Reuters request for comment.

The defect is on 787s built over the past three years, the WSJ report said, citing people familiar with the matter.

This comes as the plane-maker continues to grapple with structural defects in its 787 that have caused it to cut production and halt deliveries.

Last month, the Journal had reported that Boeing's delivery of 787 Dreamliners will likely remain halted until at least late October as the U.S. Federal Aviation Administration has rejected the company's recent proposal to inspect them.

Shares of the company were down 0.4% at $220.86 in premarket trade.