According to a report from the Seattle Times on Wednesday, the fuselage panel that blew off an Alaska Airlines jet was reinstalled improperly by Boeing (NYSE:) mechanics.

Citing a source familiar with the matter, the publication said the panel was removed for repair before being improperly reinstalled by Boeing mechanics on the Renton final assembly line.

Spirit AeroSystems (SPR) originally installed the panel into the 737 MAX 9 fuselage, but if the Seattle Times source is correct, it would mean Boeing is primarily at fault for the accident.

The incident has resulted in significant scrutiny and criticism of Boeing's quality control systems and safety culture.

The Seattle Times also noted that an anonymous whistleblower said last week that "the reason the door blew off is stated in black and white in Boeing's own records." That whistleblower is said to appear to have access to Boeing's manufacturing records of the work done assembling the specific Alaska Airlines jet.

The publication spoke with Ed Pierson, a former manager of the MAX production line and himself a whistleblower, who appeared to agree with the claims made by the previous whistleblower, saying the quality control failures were "very consistent with what I saw in the factory personally."