The body of a woman, believed to be missing grandmother Marilyn Grubb, has been found on an isolated dirt track in the outback.

NSW Police reported the discovery after a member of the public found a woman's body near a vehicle parked on a dirt track, 40km north of Broken Hill.

Police said: "Whilst formal identification is yet to take place, it is believed the body is that of a 64-year-old woman, who was last seen at a property about 50km east of Broken Hill, on Sunday 30 December 2018."

Marilyn Grubb, 64, a grandmother of 13, was last seen on December 30 after leaving a house on Menindee Road, to travel in her grey Holden the 50km to her home in Broken Hill.

When Ms Grubb didn't arrive home, her family alerted police and launched a search.

Her children and relatives made up posters and asked anyone with a dashcam or domestic CCTV to check their footage from the day between midday and 4pm.

As the days rolled on with no sign of Ms Grubb, her family said she may have travelled to the Northern Territory to visit relatives.

But at about 11am on Wednesday, a person called Broken Hill police about the body they had found near a parked vehicle on the remote track.

Police said: "At this stage it does not appear there are any suspicious circumstances.

"A post-mortem will take place and a report will be prepared for the information of the Coroner.

"Officers would like to thank members of the public and media who shared the missing person appeal."