Shares of Boeing declined nearly 2 percent on Wednesday following media reports that the FBI has joined the criminal investigation into the approval of the 737 Max 8 aircraft.

According to a report by CNBC News that cited the Seattle Times, the FBI is assisting the Federal Aviation Administration (FAA) in investigating the procedures of certifying the plane's anti-stall system known as MCAS.

Earlier, the US Department of Transportation requested its subsidiary organization check if there were illegal activities in the FAA's certification for the MCAS.

Boeing and the FAA approved the certification of the 737 Max 8 in 2017.

However, an Ethiopian Airlines plane crashed on March 10, the second Boeing 737 Max 8 model to crash in five months.

The investigation team has noted clear similarities between Ethiopian Airlines Flight 302 and Lion Air Flight 610 in the verification process of the FDR (Flight Data Recorder) data.

The Boeing Company is reportedly making efforts to update the control software of the 737 Max 8 MCAS to fix it.