A new report questions the strength of horizontal support beams in Sydney’s Opal Tower.

Authors of an interim report into concerning cracking in the newly-finished residential tower say the beams may not be strong enough to hold precast concrete panels installed on top of them.

News Corp reports say the grade of reinforced concrete used for the support beams was too low, though they also report some disagreement on this point and its contribution to the cracking.

There are now four different investigations into the cause of cracking concrete panels that have seen the building’s 300 residents evacuated twice.

The NSW Government appointed University of NSW dean of engineering Mark Hoffman and emeritus professor at the University of Newcastle’s School of Engineering John Carter for one review to be made public this week.

The NSW Government's investigation found the cracked apartment block needs “significant rectification works”.

The apartments’ body corporate has hired engineering firm Cardno to look into the problems, the builder Icon Co has engaged Rincovitch Partners for a review, and the original structural engineer for the project, WSP, is also investigating.

Residents are divided as to whether the building is safe to be reoccupied, with some choosing to stay away until more information is available.

Building firm Icon has offered reimbursements for costs associated with the evacuation.