People participate in a funeral procession alongside a lorry carrying the coffins of president Ebrahim Raisi and his seven aides in Tabriz

Tehran, May 21 (RHC)-- Iranians have gathered in Tabriz, the capital of the East Azerbaijan province, to mourn at a farewell procession for President Ebrahim Raisi, who died in a helicopter crash on Sunday.

Foreign Minister Hossein Amirabdollahian and six other people in the helicopter, including crew members, were also killed in the crash.

On Tuesday, tens of thousands of mourners, waving Iranian flags and portraits of the late president, set out from a central square in the northwestern city where Raisi was headed when his helicopter crashed.

Reporting from the capital, Tehran, Al Jazeera’s Resul Serdar said on Tuesday that funeral ceremonies for Iranian state dignitaries occur over “an extended period of time in several locations.”

After the procession in Tabriz, the bodies of Raisi, 63 and Amirabdollahian, 60, were transferred to Tehran for another ceremony.  Serdar said that later on Tuesday, the bodies would be taken to Qom, a city in central Iran of great religious significance, for another ceremony and then moved to the capital.

On Wednesday, a larger ceremony will take place in Tehran, with Supreme Leader Ayatollah Ali Khamenei expected to lead the prayers and foreign dignitaries in attendance.

Raisi’s body will then be taken to Mashhad, the country’s second largest city located in the northeast, where he was born and raised.

Organisers in Mashhad said they are planning a “glorious” burial on Thursday for Raisi in the holy city.

Reporting on the continuing investigation into the cause of the crash, Serdar said that, currently, there has been no suggestion that it was an act of sabotage, with the focus on the extreme weather conditions at the time, combined with challenging terrain and possible technical issues.

Questions have been raised as to whether Raisi and the others on board should have been travelling on a two-blade Bell 212 believed to have been decades old.

Foreign sanctions on Iran dating back to the 1979 revolution, and subsequently over its nuclear programme and its backing of the so-called “axis of resistance”, have made it difficult for the country to obtain aircraft parts or new aircraft.

Serdar said questions have also been raised as to why the aircraft was allowed to take off in adverse weather conditions which included a thick layer of fog.