Raisi journeyed through East Azerbaijan province in Iran. The incident location, near Jolfa city on the border with Azerbaijan, was approximately 600 kilometers northwest of Tehran, as reported by State TV.

Raisi had been in Azerbaijan early Sunday to inaugurate a dam with Azerbaijan’s President Ilham Aliyev. The dam is the third one that the two nations built on the Aras River.

Iran flies a variety of helicopters in the country, but international sanctions make it difficult to obtain parts for them. Its military air fleet also largely dates back to before the 1979 Islamic Revolution.

Raisi, 63, is a hard-liner who formerly led the country’s judiciary. He is viewed as a protégé of Iran’s Supreme Leader Ayatollah Ali Khamenei and some analysts have suggested he could replace the 85-year-old leader after his death or resignation from the role.