Widespread protests followed the disputed result of Iran's presidential election

The doctor who died at an Iranian detention centre holding opposition supporters was poisoned, the Iranian authorities have said.

But it was still not known if Dr Ramin Pourandarjani committed suicide or was murdered, an Iranian prosecutor said.

The coroner also revealed the person who delivered the food had been interrogated, reports said.

The 26-year-old doctor was found dead on 10 November at the Kahrizak detention centre.

"The coroner said he died after consuming medical pills, the traces of which were found in his salad," Tehran prosecutor Abbas Jafari Doulatabadi said.

Investigation

Two opposition supporters, arrested during the protests that followed disputed elections in June, died in the prison, according to officials.

But the opposition say many more have been killed in Kahrizak detention centre.

In July the prison was closed on the orders of Iran's supreme leader, Ayatollah Ali Khamenei.

In October Iranian lawmakers called for an investigation into the deaths in custody.

Following his death Iran's police chief said it was suspected he had committed suicide and that the medic was himself under investigation.

'Suspicious'

Gen Esmaeil Ahmadi-Moqaddam said a note which suggested he was feeling depressed had been found next to the body of Dr Pourandarjani.

Opposition groups and some MPs have described his death as "suspicious".

Opposition websites say he had admitted to being forced to say that one detainee had died of meningitis, and to say nothing about what he had seen.

Many of those held at Kahrizak were people who had protested against the re-election in June of President Mahmoud Ahmadinejad.

At least 30 protesters have been killed in clashes since the poll. Thousands were detained and some 200 activists remain behind bars. At least five people have been sentenced to death, prosecutors say.