The mother of jailed Iranian labor activist Mansour Osanlou has told RFE/RL's Radio Farda he has been transferred to a prison ward for drug addicts and prisoners suffering from Hepatitis and AIDS.
Osanlou's mother, Fatemeh Golqezi, said the conditions in the ward are dangerous to her son's health.
She said Oslanou, who headed Tehran's municipal bus service union, is being held at Ward 5 of Gohardasht prison in Karaj, a suburb of Tehran.
Golqezi said prison officials had explained Osanlou's transfer by saying he had planned to set fire to blankets in his cell to celebrate the Fire Festival.
This festival, part of the Iranian Norouz holiday, is traditionally celebrated with a bonfire.
"Why would a person behind bars want to light a fire?" Golqezi asked.
She said that whenever big events like the Fire Festival are happening outside, prisoners come under additional pressure from the authorities. "Isn't that enough that my son should serve a five-year prison term? Why do they put him under psychological pressure as well?" she asked.
Osanlou was arrested in July 2007 on charges of "acting against national security."
In recent months, he is reported to have been attacked several times by fellow inmates.