One person remains in a serious condition in Wellington Hospital following a fire in Akitio.
A spokesman from St John said they were called to the incident near the remote Tararua community on Tuesday around 12.28pm.
A spokesman from the fire service said they received a call from ambulance indicating there had been an explosion in a workshop on a residential property.
"By the time firefighters got there the workshop or shed had significant damage - burnt to the ground."
Two patients were then flown to Wellington hospital in helicopters with one in critical condition and the other in a serious condition.