A six-year-old girl is one of two people dead after a house fire in Sydney’s south-west, as another child fights for her life in hospital.

At about 12.40am overnight, emergency services were called to St Johns Road in Heckenberg, where a house was ablaze.

Firefighters extinguished the conflagration, which caused extensive damage to the home.

Inside, emergency services found the bodies of a six-year-old girl and a 46-year-old woman.

They are yet to be formally identified.

Eight other people – four children and four adults – who were inside at the time managed to escape the fire.

A girl and a man were taken to hospital in a critical condition.

A second child and a second man were also taken to hospital.

Police are investigating and a report will be prepared for the coroner.