The final report of the Supreme Council of the General Staff of the Iranian Armed Forces released on September 1 said that the main cause of the helicopter crash carrying Iranian President Ebrahim Raisi was the complex climate and weather conditions in the spring.
According to the investigation, "the sudden appearance of dense fog" caused the helicopter to crash into the mountain.
There were reportedly no signs of sabotage to the helicopter's components or systems.
As the helicopter entered fog on its way back from the Iran-Azerbaijan border, the pilot attempted to fly above the fog, but the engine failed to generate enough power. The helicopter then crashed into a mountainside obscured by fog.
The crash killed all nine people on board, including President Raisi and Foreign Minister Hossein Amir-Abdollahian. Iran has opened an investigation, but has found no signs of a terrorist attack.
In August, the Fars news agency reported that the main cause of the May 19 crash was bad weather conditions and the helicopter being unable to take off with two additional passengers, causing overload. However, the Iranian armed forces quickly denied this information, saying that "what was mentioned in the Fars report about the presence of two additional people on the helicopter is completely false."