A British-Australian woman detained in Iran has been identified as Kylie Moore-Gilbert, a Middle East politics specialist at Melbourne University.
She has been held for a "number of months" already, on charges that remain unclear, the Australian government says.
Dr Moore-Gilbert is the third foreign national revealed this week to have been arrested in the country.
Media reports say she has been sentenced to 10 years in jail.
"We believe that the best chance of securing Kylie's safe return is through diplomatic channels," her family said in a statement issued through the Australian government.
On Tuesday the Australian government identified two other Australians - Mark Firkin and Jolie King, who also holds a UK passport - who are also being detained in Iran.
They were blogging their travels in Asia and the Middle East and were reportedly arrested 10 weeks ago near Tehran. Their arrest is not believed to be related to that of Dr Moore-Gilbert.
All three are reportedly being held in Tehran's Evin prison, where British-Iranian woman Nazanin Zaghari-Ratcliffe has been jailed since 2016 on spying charges.
On Thursday Australia's Foreign Minister Marise Payne said the government had been working on securing their release for more than a week.
"The government have been making efforts to ensure they are being treated fairly, humanely and in custom to international norms," she said.
Dr Moore-Gilbert's profile on the University of Melbourne website says she is a lecturer in Islamic Studies who focuses on Arab Gulf states.
While the charges against her have not been disclosed, 10-year terms are routinely given in Iran for spying charges, the UK's Times newspaper said.
The situation comes amid a growing stand-off between the West and Iran - although Ms Payne said the cases of those detained were not related to diplomatic tensions.
Several people with dual Iranian and foreign nationality have been detained in Iran in recent years.
Relations between the UK and Iran have also been strained in recent months by a row over the seizure of oil tankers in the Gulf.
Australia also announced in July that it would join the US and the UK in policing the Strait of Hormuz against Iranian threats.