Fuel tankers caught fire Tuesday at a lorry park near Iran's western city of Kermanshah, sending up a plume of smoke and sparking panic among residents, state media said.
The blaze broke out during repair work to a heavy vehicle before spreading to seven others, governor Fazlollah Ranjbar said, quoted by the official IRNA news agency.
Five people including four firefighters were injured, an emergency services spokesperson told AFP.
Amateur footage aired on state television's website showed black smoke billowing into the sky above people appearing to panic as firefighters move in.
But the governor denied there was an explosion.
"We did not have any explosions anywhere in the city today and the black smoke that citizens see in the sky of Kermanshah metropolis was related to the fire in this lorry park," he said.
The blaze was contained by firefighters and rescue efforts were still ongoing, he added.
The incident is the latest in a string of explosions and fires at military and civilian sites across Iran in recent weeks.
Two blasts rocked Tehran in late June, one near a military site and the other in a health centre, the latter killing 19 people.
Fires or explosions also hit a shipyard in southern Iran this month and the Natanz nuclear complex in central Iran.
Iranian authorities said the Natanz fire was an accident, before adding they would not reveal the cause for "security reasons".