Two teenagers, who were allegedly 'huffing' from a gas bottle moments before an explosion in Mosgiel, are fighting for their lives.

Emergency services were called to a Gordon Rd house following reports of a fire shortly after 2pm.

Witnesses reported hearing two explosions, and the Fire Service has confirmed the pair had been 'huffing' prior to the explosions.

The two men - aged 18 and 19 - were assisted by residents after they ran out of the brick home on fire.

Fire Service east Otago assistant area commander Trevor Tilyard confirmed the pair were inhaling from gas bottles at the property.

Fire Service investigators and Police CIB are investigating the incident.