The evacuation alarm was raised about 2.45 p.m. on December 24 in the Sydney Opal Tower building in Sydney Olympic Park.
"An emergency services operation is underway after concerns were raised for the structural integrity of a 30-storey building at Sydney Olympic Park", police said in a statement.
The Opal Tower in Sydney was evacuated on Monday after residents reported hearing cracking noises.
"We spoke to people in the building and they got told to evacuate. they thought it was a fire".
An exclusion zone with a radius of half a mile was established around the building, forcing the evacuation of neighboring buildings and the closure of roads and a train station, Sky News Australia reported.
One of the residents told Nine News that he had heard a "big bang", as though something had "snapped" inside the building, which only opened four months ago.
Fire trucks in front of Opal Tower during an inspection by firefighters and engineers early on Christmas Day. It was unclear when those residents would be allowed back into the building, with a temporary shelter set up at a nearby hall.
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The building has shifted between one and two millimetres as a result of the issue, Police Detective Superintendent Philip Rogerson.
"They attended, identified there was a crack in the building and they called for Fire And Rescue assistance", he said.
"The building shook a little bit and we were told there was a structural damage - a crack - in the mid floor somewhere", he said.
An email to residents of a nearby apartment block said the evacuation had been ordered because "there is a potential for the tower to collapse", according to the Sydney Morning Herald.
The triangular-shaped tower has 392 apartments, a shopping area and a childcare centre.
The building has moved 1 to 2 millimeters since it was finished in August, authorities said, after they used "sensitive monitoring equipment" to test it.
The building is less than a year old and was only completed in March.