fog and strong winds, helicopters that were deployed for the search at dawn on Monday have had to be grounded, a Red Crescent official told local media.

And on Sunday, teams had to stop work altogether due to winds and snow.

The ATR 72-500 twin-engine turboprop was travelling from Tehran to the south-western city of Yasuj.

Flight EP3704 left Tehran at 04:30 GMT on Sunday, and crashed about an hour later in the Mount Dena area, about 22km (14 miles) from its destination.

image copyright Reuters image caption All 66 people on board the Iranian plane are feared dead

On Monday officials from the region told news channels rescuers had reached the site.

But both channels - IRINN and English-language Press TV - said they could not confirm the reports independently.

Later, a civil aviationspokesman told Reuters news agency the reports could not be confirmed, and then a Red Crescent official said there was "no reliable news" that the wreckage had been found.

'Grief and sorrow'

The crashed plane was 25 years old, Iran's civil aviation organisation said.

Sixty passengers, two security guards, two flight attendants and the pilot and co-pilot were on board.

Following the crash, the airline initially said that all on board had died, but later on Sunday said that it could not confirm this as no-one had reached the site.

Iran's President Hassan Rouhani expressed sympathy for all involved, saying in a statement that the incident brought "great grief and sorrow".

Supreme Leader Ayatollah Ali Khamenei said the accident "saddened the hearts".

Iran has suffered several aviation accidents in recent years and has an ageing