Mary Boyle was six years old when she went missing on 18 March 1977 whilst visiting her grandparents at Cashelard.
The dig was prompted by Danish psychic Yan Sterns, hired by country singer Margo O'Donnell - Daniel's sister - a close friend of Mary's mother, Ann.
Gardai have confirmed they were assisting the family in the fresh search near Ballyshannon.
Material taken from the ground is to be examined.
Mary Boyle is officially the Republic of Ireland's longest missing person.
The psychic visited a remote hillside near Ballyshannon on Friday and pointed to where the dig should take place.
It was his third visit to the area.
Gardai supervised the dig. They said the would act on any information supplied.
Mary Boyle disappeared 34 years ago but this is a still "a live investigation", a spokesman for the Irish police said.

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2 November 2014 Last updated at 10:11 GMT
The BBC's Ireland correspondent, Chris Buckler, reports .
A fresh dig to find the remains of a young girl who disappeared almost 34 years ago has taken place in Donegal.
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