Washington (CNN) The Transportation Department's Inspector General has opened an investigation into the Federal Aviation Administration's approval of Boeing's 737 Max planes, the Wall Street Journal reported Sunday.

The Journal's report of the inspector general's probe comes after the 737 Max planes were grounded for an indefinite period globally last week in the wake of two deadly accidents involving the aircraft model.

The investigation will be focused on an automatic safety system implicated in the October crash involving Lion Air in Indonesia, the Journal reported, citing a government official.

It is unknown if the Ethiopian Airlines flight that crashed a week ago will play any role in this investigation or not.

The Journal reported, citing a source familiar with the matter, that a subpoena has been issued by a grand jury in Washington seeking "documents, including correspondence, emails and other messages" from at least one person involved in the development of the 737 Max planes. CNN has not been able to independently verify that a subpoena was issued.

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