The Globe and Mail reports in its Wednesday edition that four bolts used to secure the panel that ultimately blew off an Alaska Airlines plane during a flight last month were removed -- and appear not to have been replaced -- at Boeing's factory in Renton, Wash., according to a preliminary report released Tuesday by the National Transportation Safety Board. A New York Times dispatch to The Globe says that the panel, known as a door plug, was opened to repair damaged rivets on the plane's fuselage. The safety board said it appeared that not all the bolts were put back once the door was reinstalled on the plane after the rivets had been repaired. As evidence, the NTSB provided a photograph of the door plug after it was reinstalled but before the plane's interior was restored. In the image, three of the four bolts appear to be missing. The location of the fourth bolt is covered with insulation. The plane was delivered to Alaska Airlines in late October. The report intensifies the scrutiny on Boeing, which has been scrambling for weeks to contain the fallout from the incident, and it raises fresh questions about whether the company did enough to improve safety after two fatal crashes of 737 Max 8 planes in 2018 and 2019.