Renton, WA - The FBI has joined the criminal investigation into the certification of the Boeing 737 MAX, lending its considerable resources to an inquiry already being conducted by U.S. Department of Transportation agents, according to people familiar with the matter.

The federal grand jury investigation, based in Washington, D.C., is looking into the certification process that approved the safety of the new Boeing plane, two of which have crashed since October.

The FBI’s Seattle field office lies in proximity to Boeing’s 737 manufacturing plant in Renton, as well as nearby offices of Boeing and Federal Aviation Administration (FAA) officials involved in the certification of the plane.

The investigation, which is being overseen by the U.S. Justice Department’s criminal division and carried out by the Transportation Department’s Inspector General, began in response to information obtained after a Lion Air 737 MAX 8 crashed shortly after takeoff from Jakarta on Oct. 29, killing 189 people, Bloomberg reported earlier this week, citing an unnamed source.

It has widened since then, The Associated Press reported this week, with the grand jury issuing a subpoena on March 11 for information from someone involved in the plane’s development, one day after the crash of an Ethiopian Airlines 737 MAX 8 near Addis Ababa that killed 157 people.

The FBI’s support role was described by people on condition of anonymity because of the confidential nature of the investigation.