A preliminary report into the fatal crash of an Ethiopian Airlines jet last month is nearing release but the exact timing is uncertain, as investigators seek to shed light on a disaster that has rocked the credibility of Boeing Co.

Ethiopia’s Transport Ministry said Monday afternoon that the report wouldn’t be unveiled Monday, contradicting a statement in the morning from the Foreign Affairs Ministry that a briefing was planned during the day. Boeing said it would review the report after release.

The March 10 crash, the second in less than five months of a Boeing 737 Max 8, triggered groundings worldwide for the aircraft and probes into how regulators cleared the plane to fly. The initial findings may explain whether the new model’s anti-stall system was to blame after it malfunctioned on a doomed Lion Air flight in Indonesia five months earlier.

According to people briefed on the probe, investigators working on the Ethiopian Airlines crash concluded that the anti-stall system had activated on the flight and they are searching for a key piece of equipment that might explain why.

Preliminary data from the Max’s black-box recorder indicates that the Maneuvering Characteristics Augmentation System, known as MCAS, was pushing the plane’s nose down during the March 10 disaster, said the people, who asked not to be named because the findings aren’t yet public.

Boeing has spent months refining the 737 Max’s software since data from the Lion Air crash indicated the stall-avoidance system had repeatedly tipped the nose down before pilots lost control. Boeing was close to a software fix when the Ethiopian Airlines jet went down.

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The MCAS was designed to keep the Max from climbing too steeply and stalling. The U.S. Transportation Department has begun an inquiry into how it was approved as part of the Max’s certification in 2017, while the Justice Department is using a grand jury to gather information.