A huge explosion rocked a gas tank filling factory leaving five workers seriously injured in Thailand.

The blast reportedly occurred right after employees had transferred liquefied petroleum gas into cylinders inside the facility in Samut Prakan province on Monday, August 29. The flammable material is believed to have leaked and was ignited by a spark, causing the violent explosion.

Staff who were sleeping in the workers' living quarters in the factory were jolted awake and fled as the fire ripped through the building. They said there were about 30 people - both Thai and foreign - inside when the incident happened.

Firefighters said they rescued 20 workers out of the factory, including the injured who were rushed to a nearby hospital.

Authorities have ordered the filling station - which has been operating for roughly a decade - closed as explosive gas still remains inside. Police officers plan to conduct investigations once the building has been cleared for entry.