Three residential buildings were completely destroyed in the blast and 15 houses in the area were damaged en people were killed and five wounded after a boiler exploded in a residential area of the city of Mashhad in northeastern Iran TEHRAN: Ten people were killed and five wounded after a boiler exploded in a residential area of the city of Mashhad in northeastern Iran, Fars News reported in a Twitter post on Saturday. Three residential buildings were completely destroyed in the blast and 15 houses in the area were damaged, according to Fars. A picture posted by Fars on Twitter showed rescue workers digging through the rubble of a building.