Firemen and rescue services have arrived at the scene, Macquarie Street has been closed to motor vehicle traffic.
"Approximately 500 people have been evacuated from the concourse and adjoining restaurants," Fire and Rescue NSW said as quoted by the News.com.au.
‘A gas company is at work and firefighters are monitoring the atmosphere for gas levels,' Fire and Rescue NSW said in a statement.
According to media reports, a gas main had been damaged during construction work. There are no reported injuries.