Police declined to say whether they were treating her death as suspicious until the post-mortem examination had been completed but there was speculation last night that she may have died from natural causes.
Ms Greig, a dental assistant from Perth, was last seen alive in the early hours of Christmas Eve after attending a party with work colleagues at the Huntingtower Hotel on the outskirts of town. Several witnesses who saw her later contacted police to say they had been concerned for her welfare.
She was eventually found by a search team in an RAF helicopter yesterday lunchtime. Police had earlier shifted the area of their operation after being contacted by a witness. Ms Greig was formally identified by her parents yesterday afternoon.
At a press conference yesterday in Perth, Detective Superintendent Ian Watson said: "We can confirm that a body was discovered at around midday in a field at Newbigging Farm, just outside Perth. An RAF helicopter was able to join the search because of a break in the weather and after an hour the crew spotted the body of a young female lying in a field.
"The body, which appears to have been lying there for some time, has not yet been identified but we have scaled down our search and we are awaiting the results of a post-mortem examination and until that happens we cannot say any more about the cause of death. I can say that her clothing was intact."
Det Supt Watson said awoman matching Ms Greig's description had been noticed walking alone along an unclassified road at about 12.30am on Christmas Eve by a local woman who was driving with her family. He said the driver had spoken to the young woman after becoming concerned that she was alone at such a late hour.
A spokeswoman for Tayside Police said: "Information received overnight has suggested that Sally may have wandered off along an unclassified road near to the Huntingtower Hotel."
Earlier her parents, Brian and Barbara, had spoken of their growing concern for their daughter. Mr Greig said: "We obviously want to find out Sally's whereabouts and if there's anything at all wrong for her to contact her mum or her dad or friends, relatives or the police - just for her to get in touch to assure everybody.
"It's out of character for Sally to have done something like this, to have gone missing. So if anyone knows anything at all please come forward."
The family were being comforted by relatives last night.Reuse content