Teen in surgery after Sydney car explosion

A teenager is in a critical but stable condition in hospital and a man has suffered facial burns after a gas bottle exploded in a car in Sydney's southwest on Sunday.

15-year-old Winston Lay, who has a shattered jaw, was brought out of an induced coma this morning and was able to respond to questions on pen and paper before going into surgery.

Emergency services were called to Fairfield about 5.30pm on Sunday where a car was found alight after a leaking gas bottle, which was in the boot, exploded when the driver lit a cigarette.

The 15-year-old boy's cousin Patrick Lai says they were about to catch the train to Vivid Light Festival in Sydney's CBD.

"Just the wrong place at the wrong time," Patrick Lai said.

It's thought Winston Lay was struck by shrapnel from a door.

His family is in shock but are thankful more people weren't injured.

The 50-year-old driver was treated for serious burns at Liverpool Hospital but has since been transferred.

Officers from Fairfield Local Area Command have established a crime scene and are investigating the incident.

Police are still examining the car but believe the incident was an accident at this stage.

Inquiries are continuing.

Police are urging anyone with information in relation to this incident to call Crime Stoppers on 1800 333 000.