At least 32 people have been killed in a fire that tore through a drug rehabilitation centre in northern Iran, authorities have said.
The blaze erupted early on Friday in Langarud, a city in the Caspian Sea province of Gilan north of Tehran.
Esmail Sadeghi, a provincial chief justice, told local media that 16 others were taken to hospital.
Iran imposes a death penalty on repeat drug smugglers and dealers but runs a series of rehab programmes for addicts.
An initial investigation showed that a heater was the cause of the fire, which then spread to the rest of the centre, the province's deputy governor was quoted as saying by the semi-official Fars news agency.
"The manager and other possible culprits have been arrested so that the cause of the incident is more accurately determined," the Tasnim news site said.
The centre accommodated up to 40 people.
Isna, a semi-official Iranian news agency, shared footage of the fire which lit up the sky and sent huge plumes of smoke into the air.
Other footage showed firefighters and ambulances gathered outside the site in the aftermath. The centre's roof had been destroyed, its windows shattered and its walls blackened by smoke.
Iran is estimated to have the world's highest per-capita number of opioid addicts and sits on a major smuggling route for opium grown in Afghanistan.
The UN Office on Drugs and Crime's world drug report this year said that Iran made 47% of the global heroin and morphine seizures originating from Afghanistan during 2020.
Amnesty International said in a June report that Iran had executed at least 173 people convicted of drug-related offences this year after "systematically unfair trials".
The figure was nearly three times more than this time last year, the rights group added.
