SEATTLE/PARIS (Reuters) Boeing anti-stall software on a doomed Ethiopian Airlines jet re-engaged as many as four times after the crew initially turned it off due to suspect data from an airflow sensor, two people familiar with the matter said.

It was not immediately clear whether the crew had chosen to re-deploy the system, which pushes the nose of the Boeing 737 MAX downwards, but one person with knowledge of the matter said investigators were studying the possibility that the software had kicked in again without human intervention.

A Boeing spokeswoman declined to comment. Ethiopian investigators were not immediately available for comment.

The Wall Street Journal reported Wednesday that the Ethiopian Airlines pilots had initially followed Boeings emergency procedures but later deviated from them as they tried to regain control of the plane.

The Journal report, citing unidentified people briefed on the matter, said the pilots had initially shut off the MCAS anti-stall system that was pushing the airplanes nose down shortly after it took off from Addis Ababa.

The pilots then cranked a manual wheel in an attempt to stabilize the plane, the report said, but they eventually decided to restore power to the usual electric trim on their control yokes, likely because the manual attempt did not achieve the desired results.