Residents of a high-rise building at Sydney's Olympic Park endured a "frustrating" night while they waited to be allowed back into their homes after a major safety scare.

The occupants of 150 units of a 392 unit complex were evacuated from their homes when an internal wall in the 36-storey Opal Tower failed.

Many residents heard "cracking" noises at the brand new complex and raised the alarm - and a full evacuation followed as authorities scrambled to discover what was wrong.

Fire & Rescue NSW Urban Search and Rescue (USAR) officers and specialist engineers worked with the building designers and building managers throughout the day and into the night to determine the integrity and safety of the affected floors.


"This is a large building and it's critical the safety of the residents comes first," said NSW Police Force Acting Assistant Commissioner Julie Boon. "Each affected floor is being assessed by engineers before we can determine if and when people can go back into their homes.

"It's been a particularly frustrating time for residents and we're very aware they are keen to go home the night before Christmas. Before that happens, police and emergency services need the building designers and engineers to be confident the building is safe to re-enter."

A temporary shelter was set up at the Sydney showgrounds for those residents who had nowhere else to go.

"It will be a long night for these residents," said Assistant Commissioner Boon. "Police and emergency services are also working with the building managers to put contingencies into place for the affected residents, if needed. Our aim is to ensure the safety of everyone involved before allowing residents to return."

Concerns were raised for the Opal Tower on Brushbox Street about 2.45pm, with occupants telling police they heard the worrying noises throughout the morning.

The building has shifted between one and two millimetres as a result of the issue, Police Detective Superintendent Philip Rogerson said.

But there has been no further movement detected on laser monitors deployed by emergency services.

Some residents had told authorities they were worried about their pets left behind in the building, but police said the number one priority was for human safety, The Daily Telegraph reported.


"In relation to pets, when we find them, they will be moved through the RSPCA to whoever we can locate tonight," Det Supt Rogerson said.

Numerous exclusion zones around the structure were established as authorities worked to establish if the building is safe.

Aerial footage by Seven Network showed fire crews setting up tents while police redirect traffic and pedestrians.

The operation would continue into the early morning with residents being kept updated by the building managers and emergency services.

The website for the Opal Tower says the building has 392 apartments, commercial spaces, a childcare centre and community centre. It cost $165 million to build.

Exclusion zones remain in place, but nearby roads have reopened.

- With wires