Regulators raise concerns about safety issues in Boeing's 737 MAX assembly line

The Boeing 737 MAX jet is currently in production in the wake of being grounded over safety issues, and now federal prosecutors are raising alarm about potential safety shortcomings on the assembly line. 

The Wall Street Journal reported Tuesday that the U.S. Department of Justice and the Federal Aviation Administration are both investigating safety problems on the assembly lines of the planes. 

Inspections found that rags and other debris was left in the fuel tanks or other interior spaces of roughly half of undelivered 737 MAX jets. Debris may be present as a result of “quality-control lapses,” according to the Journal.

The investigations being carried out are in addition to a grand jury probe of the MAX’s flight control systems, which were found to have been a key factor in two crashes that killed 346 people. 

Boeing didn’t comment on the investigations, but the company said it launched an internal investigation and took corrective actions after finding debris in undelivered 737 MAX planes.

“Safely returning the 737 MAX to service is our top priority,” Boeing said in a statement.

Boeing’s beleaguered 737 MAX jet is expected to remain grounded until at least August, sources familiar with the matter told Reuters. Earlier this month, the company said it needed to make two new software updates to the plane’s flight control computer.