Nine people were evacuated and a HAZMAT unit and a Fire and Rescue NSW unit were called to the Princes Highway building at 11.45am.

A Fire and Rescue NSW spokesman said hazardous material experts and an employee from the gas company Jemena investigated the building and found there was no gas leak.

He said they believed a smell from outside that came through the air conditioner may have caused the scare.

People were allowed back in the building an hour later.