As many as 3,000 people have been evacuated after residents of a newly completed tower block in Australia reported hearing "cracking noises".
Police, firefighters and a structural engineer inspected the building then in the neighbourhood of Sydney Olympic Park.
Fire and Rescue New South Wales reported that an emergency services operation was underway "following concerns about structural integrity of a 30-storey residential building".
"Occupants have told police they heard cracking noises throughout the morning".
FRNSW crews and Urban Search and Rescue teams are about to enter the 10th floor to investigate the source of the cracking, Fire and Rescue Acting Inspector Greg Wright said.
A resident told Nine News he heard a loud Bang, as if in the Interior of the building, something is broken.
A temporary shelter had been set up at the Sydney showgrounds for those residents who had nowhere else to go.
The triangular-shaped tower has 392 apartments, a shopping area and a childcare centre.More news: Malala is all praises for Shah Rukh Khan, ‘Zero’
Some residents of Opal Tower were also allowed to return, although not those living in the section of the building where the crack had been found.
The operator of nearby Botania tower told its residents in an email: "There is a potential for the tower to collapse, a 1km radius has been evacuated".
"I have been told by engineers it (the building) has moved one or two millimetres", detective superintendent Philip Rogerson told reporters, without going into detail.
The Opal Tower is seen at Olympic Park in Sydney, on 14 January, 2018.
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.
During the evacuation on Monday, the doors of the building became jammed and police had to break through using heavy equipment to let residents out, ABC reported.
The building was only completed in March and opened in August, and cost $165 million to build by developer Ecove, which built numerous others nearby.