NEW information about a mysterious find at the old Cairns Courthouse construction site has come to light.

On Friday construction crews working on a multimillion-dollar refurbishment of the World War I era Abbott Street building uncovered bone fragments.

More bones were dug up on Monday.

A worker at the site, managed by Cairns firm Vis Constructions, said the bones were uncovered when digging trenches for electrical cable and were found secreted within a hollow log.

The area was cordoned off and police officers were called to the site.

The heritage-listed site was acquired by Cairns Regional Council in 2016 for $5.75m to form part of a CBD art gallery precinct.

The council's general manager infrastructure services, Bruce Gardiner, said during further excavation works on Monday more bone fragments were found.

The first discovery was in the vicinity of the Abbott Street frontage about 30cm below the surface.

The second find was towards the Cairns Gallery.

"Based on the professional judgment of council's appointed archaeological team from Australian Heritage Specialists, the bones are not human, but from an animal," Mr Gardiner said.

"Police were advised of the archaeologist's determination and no further investigation was required."

Benjamin Gall, Managing Director of Australian Heritage Specialists, said it was normal for finds of this nature when working around heritage places.

"As the bones were determined to be from discarded rubbish, there have been very minimal hold ups," he said

Cairns Historical Society research assistant Jan Wegner said the Cairns Courthouse complex was among the first permanent stone building built in the emerging port city and was constructed between 1919 and 1921.

"In the early days because Cairns was founded on a series of dunes they were filing up an awful lot of swamps with rubbish," she said.

"So they became rubbish dumps and it's quite possible that the bones were part of those rubbish dumps."

Originally published as Source of mysterious courthouse bones confirmed