American detained as he 'visited his girlfriend' in Iran
Another US citizen has reportedly been detained in Iran for six months, with at least three other Americans being held in the country.
, aged 46 from California, is described as a US military veteran and was visiting his girlfriend in Iran when he disappeared in July.
White was reported missing after he failed to board a return flight via Dubai, his mother told The New York Times.
The US State Department said it was "aware of reports" that White had been detained but declined to comment further.
"We have no higher priority than the safety and security of US citizens abroad," a State Department spokesperson said.
White's mother, Joanne White, told the US daily that her son had visited Iran "five or six times" to see an Iranian woman described as his girlfriend.
The State Department told her that he was imprisoned in Iran on unclear charges.
She has asked Switzerland, which represents US interests in Iran in the absence of diplomatic relations, to pay a consular visit to her son.
White would join at least three other US citizens, two of them of Iranian descent, in being detained in the clerical-led country.
Relations between Iran and Saudi Arabia deteriorated sharply last year when US President Donald Trump withdrew from an international accord on ending Iran's nuclear programme.
Washington imposed sweeping sanctions on Tehran, which have served in emboldening conservatives in the country.
The families of those detained in Iran have said they fear Trump's combative approach towards Tehran will make it more difficult to secure their release.
Tehran has detained a number of dual nationals - a status not recognised in Iran - including Iranian-British charity worker Nazanin Zaghari-Ratcliffe.