It was not a terrorist attack or bomb explosion; it was simply a portable toilet explosion.
It happened apparently when the airman lit his cigarette there. He was rushed to hospital
with third degree severe burn.
This accident happened during the US-AustraliaTalisman Sabre joint military exercises. Cause
of explosion is still under investigation.
We know about biogas plant, where methane gas is produced by the fermentation of cow dung.
It may be an explosive gas if it is mixed with the air. Human waste can also produce methane
in the fermentation process. May be methane gas was created, mixed with the air and trapped
in that portable toilet. It exploded when came in contact of flame.