The Department of Justice has announced the opening of a criminal investigation into the possible missteps that led to a door plug blowing out of an Alaska Airlines flight in early January.

Boeing employees, including maintenance personnel, Alaska Airlines employees, and workers at Spirit AeroSystems, who assembled the fuselage of the aircraft in question, are being interviewed by the DOJ, and a grand Jury is being convened to determine whether any indictments are appropriate.

The probe was expected, according to a statement from Alaska Airlines.

“In an event like this, it’s normal for the DOJ to be conducting an investigation,” Alaska Airlines said, as reported by The Washington Post. “We are fully cooperating and do not believe we are a target of the investigation.”

Quality control and safety have been at the forefront of investigations following the January 5 incident in which a door plug blew off a flight shortly after takeoff, requiring the pilots to make an emergency landing. No serious injuries were caused by the incident that witnesses described as terrifying.

Among the findings at this point in the investigation is that Boeing failed to properly document service records on the aircraft. It is known that the plug was removed to repair damaged rivets, and a photograph has emerged showing three of the four bolts holding the plug in place missing. However, Boeing has been unable to provide service records of the repair to the aircraft that would verify whether the bolts were in place at the time of the repair. The door plug, recovered from a residential neighborhood after the incident, did not have the bolts in place, and no evidence has emerged that they were in place at the time of the incident.

“We likewise have shared with the NTSB what became our working hypothesis: that the documents required by our processes were not created when the door plug was opened,” Boeing said in a letter to Sen. Maria Cantwell (D-WA). “If that hypothesis is correct, there would be no documentation to produce.”

The DOJ will also be looking to see if Boeing violated an earlier agreement on safety issues that led to a settlement after two aircraft crashed, killing more than 300 people.

While it is not known whether the individuals who serviced the aircraft were diversity hires — or even who they are, since Boeing does not have records — the incident has fueled the pushback against diversity, equity, and inclusion (DEI) policies that have been embraced airlines and airplane manufacturers.

“Across Boeing, we continue to make progress on our commitments as we advance representation and inclusion companywide,” the company website reads. “We know diversity must be at the table for every important decision our company makes — every challenge we face, every innovation we design. Equity, diversity and inclusion are core values because they make Boeing — and each of us individually — better.”

As reported by Forbes, numerous industries are dealing with internal and external backlash over the prevalence DEI policies.

“It has become increasingly common to read comments like these from white men: ‘My promotion was delayed by three months because HR told me they had to find some Black people to interview for the position before they could give it to me,'” wrote Paolo Gaudiano, a Forbes contributor who works for Aleria, a company that conducts inclusion assessments of various businesses.