Police are investigating after a four-deck truck rollover killed more than 230 lambs near Gulargambone this morning.

Emergency services were called to Gulargambone Road at around 9:30 on 3 November, on the western outskirts of the town.

Police say the 40-year-old male driver, who the Western Plains App understands was travelling towards the town, was the sole occupant and uninjured.

There were around 465 head on board, of which police say about half died on impact, "with others euthanised at the scene by responding agencies and the owner."

"As investigations continue police are urging anyone with information about the crash – or was in the area at the time with any available dashcam/mobile phone footage – to contact Coonamble Police Station or Crime Stoppers on 1800 333 000."

The sheep were locally owned, while the driver was with a Dubbo carrier.

Services including NSW Ambulance, State Emergency Service (SES) and the Rural Fire Service attended the scene, along with Local Land Services and a veterinarian.

The owner said they expect more sheep will need to be euthanased.