CHICAGO (CBS) — Ethiopian officials have announced the pilots of a doomed Boeing 737 Max airliner followed the manufacturer’s instructions on turning off an anti-stall system that can force the plane’s nose down, but could not regain control of the aircraft before last month’s deadly crash.

Thursday morning, Ethiopian officials released their preliminary findings into the crash that killed all 157 people on board Ethiopian Airlines flight 302, putting the blame on Boeing, stating the crew followed emergency procedures provided by the company, but still couldn’t prevent the crash.

Based on the information they gathered so far, investigators said takeoff appeared very normal to pilots on board.

Investigators believe just moments before takeoff, a damaged sensor on the flight sent bad information, causing the anti-stall system, dubbed MCAS, to push the nose of the plane down, but they have not been able to find any physical damage to the sensor.

The pilots followed Boeing’s emergency procedures to shut off the anti-stall system, but could not regain control as the plane began to lose altitude.

Data from the plane’s black boxes indicate the pilots then deviated from the emergency procedures by turning back on the electronic system, which meant the MCAS kicked back into action. Over the following minutes, the MCAS is believed to have reactivated as many as four times, pushing the nose of the plane downward each time. Eventually it went into a dive and slammed into the ground outside Addis Ababa.

“In an emergency like this, that MCAS software is a monster. It comes in quick, it comes in firm, and it has a very aggressive nose-down limit,” said Dennis Tajer, spokesperson for the Allied Pilots Association.

Investigators also believe the anti-stall system contributed to the Oct. 29 crash of Lion Air flight 610 in Indonesia, which plunged into the Java Sea, killing all 189 people on board. In that flight, authorities believe erroneous data from an exterior sensor prompted MCAS to repeatedly force the nose of the plane down before the crash.

The FAA and Boeing told pilots after the Lion Air crash in Indonesia that deactivating MCAS and taking over manual control of the plane should be sufficient to prevent disaster. Boeing is now working on a software fix.

“It sounds like there may be more things that are going to need a proper review before we take on this aircraft confidently, as we did before these tragedies,” Tajer said.

Ethiopian Transport Minister Dagmawit Moges said MCAS needs to be reviewed by Boeing and aviation authorities before the plane is back in the air.

“Aviation authorities shall verify that the review of the aircraft flight control system related to flight controllability has been adequately addressed by the manufacturer before release of the aircraft to operations,” Moges said.

Boeing issued a statement Thursday morning about the Ethiopian investigation report:

“We thank Ethiopia’s Accident Investigation Bureau for its hard work and continuing efforts. Understanding the circumstances that contributed to this accident is critical to ensuring safe flight. We will carefully review the AIB’s preliminary report, and will take any and all additional steps necessary to enhance the safety of our aircraft,” Boeing President and CEO Kevin McAllister stated.

Meantime, Boeing executives must face shareholders at their annual meeting at the end of this month in Chicago. All Boeing 737 Max planes were grounded last month, and the FAA has said they won’t be allowed to fly in the U.S. again until the planes are safe.

A Chicago-based law firm represents at least 45 families of victims of the Lion Air crash in lawsuits against Boeing, and will be filing more lawsuits on Thursday in connection to the Ethiopian Airlines crash.