The cause of structural issues that triggered the evacuation of a Sydney high-rise apartment complex tower remains unclear as emergency services remain at the scene.

About three-quarters of the occupants living in the 122-apartment Mascot Towers on Bourke Street, in the inner-south Sydney suburb Mascot, were ordered out last night after concerns of ‘movement’.

But Master Builders Association executive director Brian Seidler told SBS News it’s yet to be seen whether the problem “is a question of building or design or under-design”.

“The structural integrity will be assessed firstly by the engineer, who played a role in the design of the building and the architect, the other thing is who built the building, who was the developer, there’s a whole host of pieces that have to be worked out,” he said.

“The building is 10 years old, is another issue, maintenance issues, there’s a whole host of things we have to be mindful of before a proper call can be made.”

Police and firefighters remain at the scene as the building is inspected.

“There has been some concern with movement in the building,” NSW Fire and Rescue Superintendent Adam Dewberry told AAP on Friday night.

Engineers are inspecting the decade-old building after concerns about its integrity and signs of movement, he said.

A police spokesman said there was “no immediate risk of the building collapse”.

“There have may have been an ongoing issue but it is still a matter to be determined,” he said.

Monitoring equipment is also being used on the building to help identify the issue.

“It will be a process. It won’t be a simple fix, it will be very methodical,” Supt Dewberry said.

Supt Dewberry said as the incident was “still evolving” it was yet to be determined when residents would be able to go home, or if they would need a permanent relocation.

Residents have been taken to the rear of a building on Gardeners Roads, a police spokesman said earlier.