CNN  —  The US Justice Department on Tuesday notified Boeing that it breached terms of its 2021 agreement in which the company avoided criminal charges for two fatal 737 Max crashes. After a series of safety missteps earlier this year, including a door plug that blew off an Alaska Airlines flight shortly after takeoff, the Department of Justice said Boeing is now subject to criminal prosecution. Under its deferred prosecution agreement from 2021, Boeing paid $2.5 billion in penalties and promised to improve its safety and compliance protocols. In Thursday’s letter to the federal judge overseeing the prior agreement, the Justice Department said it had notified the company that “the government has determined that Boeing breached its obligations” in multiple parts of the 2021 deal “by failing to design, implement, and enforce a compliance and ethics program to prevent and detect violations of the U.S. fraud laws throughout its operations.” The notification comes as the department conducts a new investigation into Boeing’s operations in the wake of an incident on an Boeing aircraft operated by Alaska Airlines, in which a door plug blew off while mid-flight, CNN has reported. The earlier deal had resolved an earlier fraud investigation related to the company’s development of its 737 Max aircraft. The letter to U.S. District Judge Reed O’Connor in Fort Worth, Texas, Justice Department prosecutors said: “For failing to fulfill completely the terms of and obligations under the DPA, Boeing is subject to prosecution by the United States for any federal criminal violation of which the United States has knowledge, including, but not limited to, the offense described in Paragraph 1 of the DPA and charged in the one-count Criminal Information that accompanied the DPA, or violations related to conduct described in the DPA’s Statement of Facts.”