The 17-storey Plasco Trade Center collapsed in Tehran on Thursday morning, January 19, as firefighters were trying to contain fire in the building, IRNA reported.
The incident left dozens killed or injured. Some 25 people, most of them firefighters, are still under the rubble.
'Today we mourn the loss of our brave firefighters, and pray for them and their families,' Zarif tweeted in his official Twitter account.