"It's not going to be done in minutes, hopefully it won't take longer than hours", he told reporters in Sydney.
"A few days ago the doors looked different".
This resident described feeling the Opal Tower building shake.
Some residents said the doors to the building were jammed and police had to break them down with heavy equipment to help residents escape.
A resident of the Opal Tower told the Nine News network he heard a "big bang" as if something in the building had "snapped".
An exclusion zone with a radius of 1 kilometer (half a mile) was established around the building, forcing the evacuation of neighboring buildings and the closure of roads and a train station.
Canada mounting global effort to free Canadians detained in China
The detainee, Sarah McIver from Alberta, Canada , is under administrative detention by Chinese police due to working illegally. The Huawei official was arrested after the U-S requested her extradition allegedly for violating anti-Iran sanctions.
"The number one priority for us is the safety of people-both the people inside the building and people in surrounding areas", Detective Supt Rogerson said, according to AAP.
The 36-story high-rise building was evacuated over concerns over structural instability.
"Police received a call to a loud crack on level 10 of the building located behind us", New South Wales Fire and Rescue acting superintendent Greg Wright said from outside the Opal Tower complex. They were not allowed back into their homes but were sent to an evacuation centre in central Sydney-the Royal Hall of Industries.
Some residents have returned to the Sydney Olympic Park high rise that authorities feared was at risk of collapse but it will be a grim Christmas for others after 51 units were deemed unsafe.
Wright said on December 24 FRNSW was using "laser building movement monitors" to check for any further movement. "And you do feel it [movement] sometimes when there's strong wind", he said.
Image: The Opal Tower has nearly 400 apartments.
More than 3,000 people in nearby buildings were also instructed to leave, including 55 children. It cost $165 million to build.