One set of independent experts say Sydney's cracked Opal Tower is "structurally sound" but another group is "reluctant" to advise residents to return home.

The newly-built tower in Sydney Olympic Park was evacuated on Christmas Eve after cracks were found in the building sparking fears it could collapse.

An interim report compiled by university engineering experts Mark Hoffman and John Carter and commissioned by Planning Minister Anthony Roberts was handed to the government on Friday afternoon.

AAP

"We said a week ago that our early assessment showed no evidence of any issues with the foundations of the building and our interim report will continue to support the view that the building is structurally sound," Profs Hoffman and Carter said in a statement provided to AAP on Friday.

The professors' interim report is expected to be made public within days.

A final report is still some way off as the academics continue to assess the design and construction issues as well as the scope of proposed rectification works.

"We wish to acknowledge the ongoing uncertainty and disruption for the owners and residents of the Opal Tower and assure them that we are working as quickly as possible to complete our investigation," the experts said.

The tower's builder, Icon, on Thursday stated design engineer WSP and third-party engineer Rincovich Partners had confirmed the building would be safe for reoccupation.

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It warned apartments requiring remedial work won't be ready for between one and six weeks and that it was still waiting on advice from Profs Hoffman and Carter and from Cardno - the body corporate's engineers.

Late on Friday, in a letter forwarded to residents, Cardno advised people not to return to the tower until WSP confirmed the "structural adequacy" of the building.

"Because of the considerable disruption that the completion of the major remedial works will cause to residents who may choose to return, Cardno is reluctant to recommend that residents return at an early stage," senior principal Doug McMillian wrote.

The building's strata committee has urged residents not to move back in until all experts state in writing that it is safe to do so.

"(Until then) residents should err on the side of caution," the committee wrote in an email.

"It is important to ensure that residents do not take any unnecessary risks."

An Icon spokeswoman told AAP it would continue to fund hotel accommodation for displaced residents at least until January 16 or until all experts had agreed the tower was safe to reoccupy.

AAP understands some apartment owners are already in discussions with lawyers regarding potential class-action suits against whoever is found to be liable for the tower's woes.

Icon last week defended gutting some apartments in order to install equipment propping up concrete slabs separating floors.