The Department of Justice, 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, S.C., 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 emails, 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.

[Read The Times’s investigation of safety lapses at the Dreamliner plant.]

Several employees said that in the rush to complete jets on time, managers ignored safety concerns raised by workers.