The FBI has told passengers on the Alaska Airlines Boeing 737 Max that lost a door-plug panel in midflight that they might be victims of a crime.

“I’m contacting you because we have identified you as a possible victim of a crime,” a victim specialist from the federal agency’s Seattle office wrote in the letters, which passengers received this week. “This case is currently under investigation by the FBI.”

The plane was flying 16,000 feet over Oregon on Jan. 5 when the panel blew out, leaving a gaping hole in the side. The rapid loss of cabin pressure caused oxygen masks to drop from the ceiling, and suction as air rushed from the hole exerted force on people inside the plane.

Pilots were able to land safely in Portland, Oregon, and none of the 171 passengers and six crew members were seriously injured. Investigators say it appears that four bolts used to help secure the panel were missing after the plane was worked on at a Boeing factory in Renton, Washington.