The body was found in a large shed to the rear of a farm property in the Killoughter area, north of Ashford, near Newcastle, Co Wicklow.
It was unclear if the woman died at the scene. Her remains were located under a tarpaulin.
Ms Shortall, 47, was last seen on Good Friday at around 4pm in Leitrim Place, Wicklow Town.
Following the discovery of the body, a 38-year-old man was arrested at the scene and was being held last night in Wicklow Garda Station under Section 4 of the Criminal Justice Act.
The scene where the body was found was preserved for a full Garda technical examination. A second scene was preserved in Wicklow Town.
The search for the missing woman was stood down yesterday afternoon, although gardaí did not confirm if the body was that of Ms Shortall.
Earlier in the day, volunteers had been involved in a search close to the Murrough, a 15km-long coastal wetland area, extending north of Wicklow Town as far as Greystones.
Gardaí joined family, friends, and members of the coastguard and Civil Defence to comb the area. Superintendent Paul Hogan thanked everyone for their co-operation when news emerged that a body had been found.
“Our thoughts and prayers are now with the Shortall family,” he said. Professor Marie Cassidy, the state pathologist, arrived to carry out a preliminary examination shortly before 5pm.
The woman’s body was subsequently taken to Loughlinstown Hospital where a full autopsy will take place today.
Anyone with information in relation to the investigation is asked to contact Wicklow Garda Station on 0404 60140, The Garda Confidential Line on 1800 666 111 or any Garda Station.
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