Media sources reported that the sound was heard in Garmsar industrial town.
According to Bahman Behnam Bakhtiari, Director General of Industry, Mining and Trade of Semnan province, the aid teams have been sent to the industrial town.
He also added that the cause of the explosion has not been determined yet.
So far, no smoke or trace of the explosion has been observed in Fajr Industrial Town, he also said.
Reza Khani, the governor of Garmsar also said that the details of the incident will be announced soon.
RHM/