The US department of justice has launched a criminal investigation into the Boeing jetliner blowout that left a gaping hole on an Alaska Airlines plane this January, the Wall Street Journal reported.

Citing documents and other sources, the newspaper said investigators have contacted some passengers and crew – including pilots and flight attendants – who were on the January 5 flight.

The Boeing plane used by Alaska Airlines suffered the blowout seven minutes after take-off from Portland, Oregon, forcing the pilots to make an emergency landing.

Boeing has been under increased scrutiny since the incident, when a panel that plugged a space left for an extra emergency door blew off a Max 9 jet. There were no serious injuries.

Alaska Airlines said in a prepared statement: “In an event like this, it’s normal for the DoJ to be conducting an investigation.

“We are fully co-operating and do not believe we are a target of the investigation.”

The Journal reported that the investigation would assist the Department’s review of whether Boeing complied with a previous settlement that resolved a federal investigation into the safety of its 737 Max aircraft following two deadly crashes in 2018 and 2019.

In 2021, Boeing had agreed to pay 2.5 billion dollars (£1.9 billion), including a 244 million dollar (£190 million) fine, to settle an investigation into the crashes of flights operated by Lion Air and Ethiopian Airlines. The company also blamed two employees for deceiving regulators about flaws in the flight-control system.

Boeing has acknowledged in a letter to US congress that it cannot find records for work done on the door panel of the Alaska Airlines plane.

“We have looked extensively and have not found any such documentation,” Ziad Ojakli, Boeing executive vice president and chief government lobbyist, wrote to senator Maria Cantwell on Friday.

The company said its “working hypothesis” was that the records about the panel’s removal and reinstallation on the 737 MAX final assembly line in Renton, Washington, were never created, even though Boeing’s systems required it.

The letter, reported earlier by The Seattle Times, followed a contentious Senate committee hearing on Wednesday in which Boeing and the National Transportation Safety Board argued over whether the company had co-operated with investigators.

The safety board’s chair, Jennifer Homendy, testified that for two months Boeing repeatedly refused to identify employees who work on door panels on Boeing 737s and failed to provide documentation about a repair job that included removing and reinstalling the door panel.

“It’s absurd that two months later we don’t have that,” Ms Homendy said.

“Without that information, that raises concerns about quality assurance, quality management, safety management systems” at Boeing.

Ms Cantwell, a Democrat from Washington, demanded a response from Boeing within 48 hours.