Tehran Emergency Medical Services spokesman Tabrizi said the fire was reported at 12:56 pm local time, prompting the immediate dispatch of seven ambulances, an ambulance bus and a command vehicle to the scene.
He said 18 people were injured, with four transferred to hospitals while the remaining victims received treatment at the site. No fatalities have been reported so far.
The spokesman added that a nearby emergency medical station was destroyed by the blast wave. However, its personnel were away on a mission at the time of the explosion and were unharmed.
Davoud Vali, a member of the board of directors of the Shamsabad Industrial Estate, said the incident began when a fuel storage tank caught fire at one of the industrial units before exploding.
The blast caused the fire to spread to other sections of the facility, expanding the scope of the blaze, he added.
Meanwhile, Bijan Soleimanpour, deputy governor of Tehran Province and special governor of Rey County, dismissed speculation circulating about the cause of the explosion.
Contrary to some rumors, he said, the incident was not related to any projectile strike or external factor. According to the official, the explosion occurred in a tank containing industrial materials at a manufacturing unit.
Soleimanpour said no deaths had been reported and that experts are investigating the exact cause of the explosion as well as the extent of the damage.