The official said the lives of Raisi and Foreign Minister Hossein Amirabdollahian were "at risk following the helicopter crash", which happened on the way back from a visit to Iran's border with Azerbaijan.
"We are still hopeful but information coming from the crash site is very concerning," said the official, speaking on condition of anonymity.
The bad weather was complicating rescue efforts, the state news agency IRNA reported. The chief of staff of Iran's army ordered all the resources of the army and the elite Revolutionary Guard to be put to use in the search and rescue operations.