They said the gas pipeline along a highway linking the provincial capital of Ahvaz to the city of Mahshahr caught fire after the blast on Thursday morning, killing 5 people and injuring 6 others.
Governor of Ahvaz said the blast set ablaze a bus, a water tank truck, and two sedans, noting that the bus was fortunately not carrying any passengers.
Jamal Alami ruled out the possibility of a terrorist attack, saying the incident was caused by a gas leak.
He also noted that the fire has not caused any damage to nearby villages and farms.
Meanwhile, head of the fire department of Ahvaz said the death toll may rise given the magnitude of the fire.