NEW YORK (NYTIMES) - The US Justice Department, which has been looking into problems with Boeing's 737 Max jet, has broadened its investigation to include the production of the company's 787 Dreamliner, according to two people familiar with the matter.
Federal prosecutors recently subpoenaed Boeing for documents related to production processes at the Dreamliner plant in North Charleston, South Carolina, the people said.
In April, The New York Times detailed allegations of shoddy work and flawed quality control at the factory that threatened to compromise safety.
The article, based on hundreds of pages of internal e-mails, company documents and federal records, revealed that debris was regularly left inside aircraft. A ladder was found in a plane's tail and a stray bolt in an engine.
Several employees said that in the rush to complete jets on time, managers ignored safety concerns raised by workers.
The Federal Aviation Administration (FAA) confirmed three safety complaints lodged by employees at the plant since September, according to an FAA official and an internal agency e-mail.
Boeing declined to comment on the inquiry by the Justice Department. The investigation into the Dreamliner was reported by The Seattle Times.
Federal prosecutors and investigators at the Transportation Department's inspector-general have been looking into the development of the Max after two of the jets crashed within five months, killing 346 people.
The new focus on the Dreamliner is a sign that the investigation is widening into engineering development and production at Boeing factories in Washington state and South Carolina.
A month after the New York Times article, the executive in charge of the troubled plant, Mr David Carbon, stepped down. An internal Boeing memo said Mr Carbon was leaving "to care for his family" after several years as vice-president for 787 operations at Boeing South Carolina.
Many of the employees said Mr Carbon had fostered a culture that at times made speed a priority over safety.
An inspector for American Airlines found so much debris inside Dreamliners made at the plant that he began collecting it in small plastic storage bags to show Mr Carbon. The inspector once discovered a bolt inside an engine of a plane that had gone up for a test flight. He also found Bubble Wrap near the pedal that pilots used to control the plane's rudder.
In response to the allegations, Boeing said its planes go through multiple safety tests before they begin flying.
"Boeing and the FAA implement a rigorous inspection process to ensure that all our airplanes are safe and built with the highest levels of quality," Mr Gordon Johndroe, a Boeing spokesman, said.
But current and former employees at the plant told The Times that it had been plagued by problems for nearly a decade.
They described metal shavings being left underneath floorboards, near critical electrical systems that control the Dreamliner. A ladder and a string of lights were left inside tails, dangerously close to the gears that control the horizontal stabiliser. Defective parts have been installed on airplanes.
Officials believe that the metal shavings may have caused damage to an airplane that was already in service in 2012, according to two people with knowledge of the matter.
The FAA is also investigating an incident in which a manager at the Charleston plant inappropriately pressured an employee involved in certification. The Boeing employee is a member of a team designated by the FAA to help certify aircraft.
In a letter sent to Boeing on June 6, the FAA said that the employee "experienced interference from management". The letter, portions of which were reviewed by The Times, also said that rules for delegating certification to Boeing "are not being followed, or alternatively are being subverted".
Boeing production managers are not allowed to intervene in the work of employees who are supposed to represent the FAA.
At the Charleston plant, the employee had two managers, one within the designee programme and another outside it, according to FAA documents. Such a reporting structure is typically considered a violation of agency rules.