A search and rescue operation is underway after a helicopter carrying Iranian President Ebrahim Raisi crashed in a mountainous region.

While no report has so far emerged about Raisi’s fate, here is what happens when a president passes away while still in office in Iran.

In Iran the Supreme Leader, a title currently held by Ali Khamenei, is considered the biggest authority in the country. The president is considered to be the second-in-command.

However, in the event of a president’s death, the vice-president of the country takes the reins.

New presidential elections are required to be held within 50 days.

The current vice-president is Mohammad Mokhber. Hours after Raisi’s helicopter was reported to be missing, Mokhber himself set off for the crash site.

Mahjoob Zweiri, a professor at Qatar University, described Raisi as a prominent figure in Iranian politics in a comment with Al-Jazeera.

Zweiri further suggests that Raisi is being considered as a possible future successor to Iran’s Supreme Leader, Ayatollah Ali Khamenei.