WASHINGTON -- The Federal Aviation Administration said on Monday it has opened an investigation into the Boeing 787 Dreamliner after the planemaker said some employees had committed "misconduct" by claiming some tests had been completed.

The FAA said it is investigating whether Boeing completed the inspections to confirm adequate bonding and grounding where the wings join the fuselage on certain 787 Dreamliner airplanes "and whether company employees may have falsified aircraft records."

The agency said "at the same time, Boeing is reinspecting all 787 airplanes still within the production system and must also create a plan to address the in-service fleet."

Boeing shares were down 1.5 percent at $177.03 late on Monday afternoon.

Asked for comment, Boeing provided an April 29 email from Scott Stocker, who leads the company's 787 program, to employees in South Carolina where the 787 is assembled.

In the email, Stocker said that an employee saw what appeared to be an irregularity in a required 787 conformance test.

Stocker said in the email that after receiving the report, "we quickly reviewed the matter and learned that several people had been violating Company policies by not performing a required test, but recording the work as having been completed."

Stocker said Boeing promptly informed the FAA "about what we learned and are taking swift and serious corrective action with multiple" employees.

He added, "our engineering team has assessed that this misconduct did not create an immediate safety of flight issue."

Boeing said in April it expects a slower increase in the production rate and deliveries of its 787 Dreamliner widebody jets as the company wrestles with supplier shortages "on a few key parts.”

A Boeing quality engineer recently criticized some of the manufacturing practices on the 787 and 777 widebody programs and testified last month before Congress.

The Justice Department is conducting a criminal investigation into a Jan. 5 mid-air emergency of a Boeing 737 MAX 9.

The National Transportation Safety Board has said four key bolts appeared to be missing from the plane that had been delivered by Boeing months earlier. Boeing has said it believes required documents detailing the removal of the bolts were never created.