Police have cordoned off the house and police officers are stationed outside the property in east Orange.

Officers from the Central West Police District attended the house at about 7.30pm on Thursday after receiving reports of a concern for welfare.

Officers gained access to the home where they found a three-year-old girl dead and her 40-year-old mother in a semi-conscious state.

NSW Ambulance paramedics were called to the scene and the woman was taken to hospital for further treatment.

A crime scene has been established at the home with police tape around the property and an investigation is now underway by detectives from Central West Police District.

Anyone with information about this incident is urged to contact Crime Stoppers: 1800 333 000 or https://nsw.crimestoppers.com.au. Information is treated in strict confidence. The public is reminded not to report crime via NSW Police social media pages.