Iranians gather at the site where a 10-storey building collapsed as rescue operations continue in the southwestern city of Abadan. AFP
A large section of the 10-storey Metropol building that was under construction in the city of Abadan, Khuzestan province, crashed to the ground on Monday, with initially dozens feared trapped.
"The exact number of people trapped under the rubble is not known, but so far, the bodies of 18 people have been recovered," state news agency IRNA quoted city governor Ehsan Abbaspour as saying.
He added that "37 people were rescued from the rubble and taken to city hospitals for treatment", with most of them now discharged.
The search and rescue operation will continue "until the last body is recovered," said Abbaspour.
Interior Minister Ahmad Vahidi, who was in Abadan, earlier told a state broadcaster that the search was moving slowly and carefully because of the risk adjacent buildings would also collapse.
The provincial judiciary said at least 10 people were arrested, including the mayor and two former mayors, accused of being "responsible" for the collapse, state TV reported online.
An investigation has been opened into the cause of the disaster in Abadan, a city of 230,000 people, 660 kilometres (410 miles) southwest of the capital Tehran.
In a previous major disaster in Iran, 22 people, including 16 firefighters, died in a Tehran blaze that engulfed the Plasco building, a 15-storey shopping centre, in January 2017.