Boeing has acknowledged in a letter to Congress that it cannot find records for work done on a door panel that blew out on an Alaska Airlines flight over Oregon two months ago.

"We have looked extensively and have not found any such documentation," Ziad Ojakli, Boeing executive vice president and chief government lobbyist, wrote to Sen. 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 Wednesday in which Boeing and the National Transportation Safety Board argued over whether the company had cooperated 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," Homendy said. "Without that information, that raises concerns about quality assurance, quality management, safety management systems" at Boeing.

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

Shortly after the Senate hearing, Boeing said it had given the NTSB the names of all employees who work on 737 doors — and had previously shared some of them with investigators.

In the letter, Boeing said it had already made clear to the safety board that it couldn't find the documentation. Until the hearing, it said, "Boeing was not aware of any complaints or concerns about a lack of collaboration."

Boeing has been under increasing scrutiny since the Jan. 5 incident in which a panel that plugged a space left for an extra emergency door blew off an Alaska Airlines Max 9. Pilots were able to land safely, and there were no injuries.

In a preliminary report last month, the NTSB said four bolts that help keep the door plug in place were missing after the panel was removed so workers could repair nearby damaged rivets last September. The rivet repairs were done by contractors working for Boeing supplier Spirit AeroSystems, but the NTSB still does not know who removed and replaced the door panel, Homendy said Wednesday.

The Federal Aviation Administration recently gave Boeing 90 days to say how it will respond to quality-control issues raised by the agency and a panel of industry and government experts. The panel found problems in Boeing's safety culture despite improvements made after two Max 8 jets crashed in 2018 and 2019, killing 346 people.