Investigation comes amid heightened scrutiny of Boeing’s safety record following fatal crashes in 2018 and 2019.

The Department of Justice (DOJ) has interviewed witnesses including aircrew as part of the probe into the January 5 incident in which a portion of the fuselage blew off mid-flight, the Wall Street Journal and The Washington Post reported on Saturday.

Alaska Airlines said it was cooperating with authorities.

“In an event like this, it’s normal for the DOJ to be conducting an investigation. We are fully cooperating and do not believe we are a target of the investigation,” Alaska Airlines said in a statement to Al Jazeera.

Boeing did not immediately respond to a request for comment.

The investigation comes as Boeing is under scrutiny over its safety record following a series of incidents, including two fatal crashes involving the Boeing 737 MAX in 2018 and 2019.

The DOJ probe will inform authorities’ assessment of whether Boeing has complied with the terms of a $2.5bn settlement to avoid prosecution in relation to those crashes, the Wall Street Journal reported.

On Monday, the US Federal Aviation Administration (FAA) said it had identified “non-compliance issues in Boeing’s manufacturing process control, parts handling and storage, and product control” following an audit of the company that included interviews with employees and a visit to its production line.

The FAA said Boeing would have 90 days to come up with a plan to correct the issues.

A separate FAA report, released last month but launched before the blowout incident, found serious problems with Boeing’s safety culture, including fears of retaliation among employees with safety concerns.

Boeing said in a letter to the US Congress on Friday that it was unable to locate records for work carried out on the door panel that fell off the Alaska Airlines plane.

The Seattle-based aircraft manufacturer has said it believes that records about the panel were never created despite company rules requiring such documentation.