Residents of the Opal Tower apartment building at Sydney Olympic Park have been evacuated amid "cracking noises".
An emergency operation is now under way, with residents evacuated and an exclusion zone set up that includes the train station.
About 2.45pm on Monday concerns were raised over the structural integrity of the 30-storey residential building on Brushbox Street.
A number of residents left the building of their accord, police said in a statement.
Fire and Rescue NSW and police are now assisting people to evacuate the building, and exclusion zones are in place along number of nearby streets.
Trains are not running between Lidcombe and Sydney Olympic Park as a precaution.
Aerial footage shows fire crews setting up tents while police redirect traffic and pedestrians.
Australia Ave is closed in both directions at Bennelong Pkwy due to a police operation. Traffic is being diverted into Sarah Durack Ave.
Specialist rescue trucks with building movement sensors on them are now on the scene and more emergency resources are on the way.