Neighbours have left flowers at the entrance to a northern NSW property where twin girls died following a house fire thought to have started after a candle was left burning.

Police and ambulance paramedics performed CPR on the four-year-old sisters but they were unable to be revived.

Chief Inspector Mick Dempsey said the girls had been asleep as the fire started.

“They were found to be unresponsive,” he told Seven News.

“CPR was performed by police and ambulance personnel but unfortunately the two children could not be revived and they have since passed away.”

A woman was also being treated for shock.

Emergency services were called to the single-storey residence on Mafeking Road in the hamlet of Goonengarry, west of Byron Bay, just after 4am on Sunday after reports two children were suffering from smoke inhalation.

Insp Dempsey said a number of adults were outside the premises, in the vicinity of the house, as the drama unfolded.

There was limited damage to the structure of the premises. However there was some evidence of smoke having filled the bedroom, he added.

The building is part of a multiple-occupancy community, police say.

A bouquet of flowers was left outside the entrance to the property on Sunday afternoon with a note that read: “No words mourning with you.”

Detectives will work with fire investigators to determine the cause of the blaze but say initial reports suggest to them that a candle may have been left burning inside the home.

-AAP