Investigators into a Boeing 737 MAX crash in Ethiopia that killed 157 people have reached a preliminary conclusion that an anti-stall system was activated before the plane hit the ground, the Wall Street Journal reported on Friday, citing people briefed on the matter.

US safety investigators have reviewed data from the "black boxes" that were aboard Ethiopian Airlines Flight 302, four people briefed on the investigation told Reuters on Thursday. A preliminary report is expected as early as next week, the US officials said.

The plane crashed on March 10 shortly after taking off from Addis Ababa.

Investigators into a deadly 737 MAX crash in Indonesia in October have also focused on the new anti-stall system, called MCAS. Boeing on Wednesday said a planned software fix would prevent repeated operation of the system that is at the centre of safety concerns.

Boeing's fastest-selling 737 MAX jet, with orders worth more than $500 billion at list prices, has been grounded globally by the Federal Aviation Administration (FAA), although airlines are still allowed to fly them without passengers to move planes to other airports.