United Airlines has found loose bolts and other parts on 737 Max 9 plug doors as it inspects its fleet of Boeing jets following the Friday rapid depressurization aboard an Alaska Airlines jet of the same make, according to three people familiar with the findings.

The discrepant bolts and other parts on the plug doors have been found on at least five aircraft, one of the people told The Air Current.

A Boeing representative did not immediately respond to a request for comment. A spokeswoman for the Federal Aviation Administration declined to comment on the United findings, and pointed to the agency’s earlier statements.

United confirmed the findings in a statement, saying, “Since we began preliminary inspections on Saturday, we have found instances that appear to relate to installation issues in the door plug – for example, bolts that needed additional tightening. These findings will be remedied by our Tech Ops team to safely return the aircraft to service.”