A helicopter carrying President Ebrahim Raisi crashed on Sunday, according to Iran’s state media and the country’s mission to the United Nations, but has yet to be found by search-and-rescue workers because of heavy fog.

The helicopter was also carrying Hossein Amir Abdollahian, Iran’s foreign minister.

The state news agency IRNA reported that an enormous search operation involving 16 teams was underway to locate the helicopter. Inclement weather, the reports said, was hampering the effort. The teams had yet to locate the crash site after almost five hours.

State media has yet to report on casualties or confirm the whereabouts or condition of the president. The cause of the crash is also unknown.

“Given the complexities of the region, connection has been difficult, and we are hoping that the rescue teams reach the helicopter and can give us more information,” Ahmad Vahidi, Iran’s interior minister, told state television.

Mr. Raisi was on an official visit to the province of Western Azerbaijan, a mountainous region in northwestern Iran.

A delegation of ministers traveled with him in a convoy of three helicopters, state media reported, adding that the two other aircraft had reached their destinations.

In addition to the president and the foreign minister, the governor of the province was also in the helicopter, which crashed in an area called Varzaghan, state media reported.

Iran’s law stipulates that if the president dies, power is transferred to the first vice president and an election must be called within six months. The first vice president is Mohammad Mokhber, a conservative politician.