Iran has arrested the person who filmed the footage showing the Ukrainian passenger plane being shot down by a missile.
It is believed the person being detained will face charges related to national security.
Flight PS752 was brought down after it took off from Tehran on January 8, killing all 176 people on board.
Iran has said it was shot down unintentionally and announced the arrest of several people over the incident.
President Hassan Rouhani said his country’s investigation would be overseen by a “special court”.
He said in a speech: “This will not be a regular and usual case. The whole world will be watching this court.”
President Rouhani also stressed that the “tragic event” should not be blamed on one individual.
He said: “It’s not only the person who pulled the trigger, but also others who are responsible.”
Iran initially denied that the passenger jet was hit by a missile, but later conceded that the aircraft was hit by its air defense systems.
When the video was shared on social media, it led analysts to say it showed the plane was hit by a missile.
Iranian media reported that the country’s elite Revolutionary Guards had taken a person who posted a video last week of the missile striking the plane into custody.
However, an Iranian journalist based in London who initially posted the footage has insisted that his source is safe, and that the Iranian authorities have arrested the wrong person.
On January 14, Iranian judiciary spokesman Gholamhossein Esmaili said that several people had been detained over the downing of the plane.
He added that about 30 people had been arrested for “taking part in illegal gatherings” – an apparent reference to recent anti-government protests.
Separately the New York Times said security camera footage showed two missiles were fired at the plane, more than 20 seconds apart.
The paper said this would explain why the plane’s transponder seemed to have stopped working before the missile strike – it had been disabled by the first missile.