A draft interim report from Ethiopian crash investigators sent to US agencies claims the March 2019 crash of a Boeing 737 MAX was caused by the plane's design, sources have told Reuters.
Unlike most interim reports, this one includes a probable cause determination, conclusions and recommendations, which are typically not made until a final report is issued.
The US National Transportation Safety Board (NTSB) has been given a chance to lodge concerns or propose changes, the sources claimed.
Reuters agreed not to reveal their identities.
NTSB spokesman Eric Weiss confirmed the agency had received the draft interim report from investigators in Ethiopia but declined to comment on whether the agency would suggest any changes.
The report is said to focus directly on the aircraft manufacturer and says little or nothing about the performance of Ethiopian Airlines or its flight crew, and that has raised concern with some participants in the investigation.
The Ethiopian interim report contrasts with a final report into the Lion Air crash released last October by Indonesia which faulted Boeing's design of cockpit software on the 737 MAX but also cited errors by the airline's workers and crew.
Ethiopian Airlines flight 302 crashed in an open field six minutes after take-off from Addis Ababa, the Ethiopian capital, killing 157 passengers and crew. The Boeing 737 MAX has been grounded worldwide for nearly a year after the two fatal crashes.
Under rules overseen by the United Nations' Montreal-based aviation agency, ICAO, Ethiopia should publish a final report by the first anniversary of the crash on March 10 but now looks set to release an interim report with elements that would normally be included in the final report.
A preliminary accident report by the Ethiopian Civil Aviation Authority released in April last year said faulty sensor readings and multiple automatic commands to push down the nose of a Boeing plane contributed to the fatal crash and left the crew struggling to regain control.
Last week the US House Transportation Committee released preliminary investigative findings into the two crashes which faulted the Federal Aviation Administration's approval of the plane and Boeing's design failures, saying the 737 MAX flights were "doomed".