Two teenagers were treated for minor burns  to their head and hands after a gas bottle exploded and sparked a fire at a Penshurst youth refuge on Sunday afternoon, police said.

Mortdale and Hurstville fire brigades were called to the refuge and extinguished flames on an outdoor pergola about 4pm.

The fire is not being treated as suspicious and police believe it was sparked by flames from a barbecue and an adjoining gas bottle.