Boeing Co and U.S. regulators said Thursday that some titanium 787 Dreamliner parts were improperly manufactured over the past three years.

"The sub-supplier is under scrutiny by prosecutors therefore Leonardo is injured party and will not bear any potential costs associated with this issue," the Italian state-controlled defence group said in a statement.

Leonardo added that the company, Manufacturing Processes Specification (MPS), was no longer its supplier.

The company did not immediately respond to a request for comment.

(Reporting by Francesca Landini, writing by Giulia Segreti)