The cause of a large blast in Iran's Semnan province was determined as a fighter jet breaking the sound barrier on Monday, state media reported.
Iranian state media had earlier said a large explosion was heard at the Garmsar industrial town, the fourth such incident in the province of Semnan in a week, according to the semi-official Mehr news agency.
"Upon investigating, officials announced that no explosion or smoke was observed from the Garmsar industrial area," state media said.
"It is now known that the cause of the blast was a fighter jet breaking the sound barrier in the area after flying its jet below the permissible speed," state media added, without specifying whether the jet was Iranian.