An investigation is under way after a grisly discovery inside a suitcase on the side of the road in southern NSW.

Police were called to Wolgon Road at Oallen, about 60 kilometres south-east of Goulburn, on Sunday.

Two passersby had reportedly come across the body and reported it to police.

Officers who arrived on scene uncovered human remains inside a suitcase. It reportedly may have been there fore some time.

The body was believed to be female. It has not yet been identified.

The suitcase was seized to undergo forensic examination and a crime scene was established.

Hume Police District Superintendent Linda Bradbury told ABC 702 Sydney that police were trying to identify the remains.

“That is still under way as they are in a state of decomposition, so that will take some time,” she said.

“Forensic examination is under way to assist us in identifying how long that suitcase has been there.”