Subsequently, police made the emergency declaration under the Public Safety Preservation Act, with an exclusion zone surrounding the accident site.
The boundaries of the exclusion zone encompass the New England Highway from Aerodrome Road to High Street, including Mayfair Lane and Melaluca Crescent.
Motorists are being urged to avoid the area.
Applethorpe is located on Queensland’s western border with New South Wales, and is about 213 kilometres south-west of Brisbane.