Iranian authorities have denied that an American-Iranian dual national died on Saturday owing to a lack of medical attention at Tehran’s notorious Evin jail.
Faramarz Javidzad, 60, was brought to hospital after suffering gastrointestinal bleeding, according to BBC Persian, but was subsequently returned to prison.
Officials refused to transport him from the jail clinic when his blood pressure plummeted dramatically on Friday.
The US stated that it was aware of the death of a person in an Iranian jail.
The announcement comes only a week after Iran freed five other American-Iranian prisoners as part of a prisoner swap.
The Iranian judiciary’s Mizan news agency cited Tehran province’s prisons department as saying on Monday that Mr Javidzad had been detained for two months at Evin on various financial charges, and that he was treated five times for digestive problems during that time.
He recently underwent a stomach operation and was then discharged from hospital “at his own insistence”, it added.
The prisons department said Mr Javidzad was immediately transferred to hospital when his condition worsened on Saturday. Doctors and nurses administered CPR, but his life could not be saved, it added.
However, the account was contradicted by the source who spoke to BBC Persian’s Ali Kheradpir.
They said Mr Javidzad was put on a drip at the prison’s clinic on Friday after his blood pressure dropped, even though a judge had given prison authorities permission to transfer him to hospital.
That night, a nurse at the clinic informed him that they were “sleepy” and removed the drip, they added.
On Saturday, Mr Javidzad’s condition worsened and he died while awaiting transfer to hospital, the source added.
A spokesperson for the US state department told BBC News: “We are aware of reports of the death of an individual in an Iranian prison and are seeking additional information.”
“Due to privacy considerations, we have no further comment at this time.”
BBC Persian reported that the state department had not designated Mr Javidzad as “wrongfully detained” by Iran, which meant he was not included in last week’s prisoner exchange.
It saw Iran free five American-Iranian dual nationals, who the US said had been imprisoned on baseless charges for political leverage.
In return, the US granted clemency to five Iranians imprisoned in US jails and allowed $6bn (£4.8bn) of frozen Iranian funds held in South Korea to be transferred to banks in Qatar for humanitarian purchases.