An independent investigation into Sydney's cracked Opal Tower has found numerous factors could have caused the cracking.
An interim report into Sydney's cracked Opal Tower has found several factors could have contributed to the building's problems, but has ruled out extreme weather and dodgy materials.
The independent report, commissioned by the NSW government and released on Tuesday, found the building is structurally sound but will require "significant rectification works".
"While we have isolated the probably cause to localised structural design and construction issues, we need more information to make definitive conclusions about the cause or causes of the damage," the report's authors said.
"More work is also needed before we can provide recommendations on what needs to happen to avoid incidents like this in the future."
The team of professors, who visited the site multiple times during their investigation, suggested a number of things be checked before major rectification works begin and residents move back in.
"We recommend that independent and qualified structural engineers be engaged to check final proposals in detail before major rectification works begin," they said, adding it is difficult to say how long that could take.
The Opal Tower in Sydney's Olympic Park was evacuated on Christmas Eve after residents noticed cracking in parts of the building.