A Mount Maunganui wood working factory worker is at Waikato Hospital receiving treatment for burns he received during an explosion and fire at the facility.

The 63 year old man was first taken to Tauranga Hospital late this morning, but was later transferred to Hamilton.

Firefighter extinguishes the hopper fire.

A second man, also aged 63, was also initially taken to Tauranga Hospital with burns, but was subsequently discharged.

The two men were checking a Hocking Street joinery factory's dust extraction system at about 11am when the first explosion took place, says Tauranga fire senior station officer Phil Price.

'That shipping container was being used as a hopper to receive sawdust from the big bag tower,” says Phil.

'They were investigating the fan that was blowing the dust into that container from the bag tower – they thought a piece of wood or something had got stuck in it.

'They could smell burning. They were investigating that and were just shutting the system down when the container exploded.”

The explosion injured the two men who were standing nearby. Mount Maunganui St John paramedic Chris Jones says they suffered flashover burns.

He treated a man with burns to his forearms, backs of his hands, face and scalp.

He praised the efforts of the Trayco staff who did a great job continuing to pour water over the men's burns in the sink, and by pouring a water cooler bottle over the face and scalp of one of the men.

'Somebody reported a large fireball rolled out of the front of the container which sounds right to me,” says Phil.

'On the way there we could see a big cloud of white smoke over the area.”

The fire service was called when the sprinklers activated. Then they began receiving the 111 calls saying there had been and explosion and people injured.

'That was the first explosion, the big one – then there were three subsequent explosions.

'That container was connected by a big duct back to the bag tower.

'The explosion went up the pipe and has caused three secondary explosions in the bag tower.

'Fire broke out in there which was contained by the sprinkler system.”

Workmates took the two men to the front of the building and started pouring water on their burns while others used a building hose to try and put out the fire in the container.

The hopper was moved across the yard by forklift to make it easier for fire fighters to access it.

The explosion just before 11am alerted neighbours at Interclean who looked over the fence to see a man near the container door, who was forced back by a wall of flame.

'A ball of flames came out and he just ran,” says a witness.