"Following information on social media, police conducted an operation in the vicinity of the Opera House and Manly as a precautionary measure," police said after concluding operations in the area.
The forecourt of the OperaHousewas evacuatedat around 2 PM (local time) andpolice erected metal barriers.
All tours of the Opera House were also cancelled for the day and ferries were either delayed or cancelled.
Crowds were told to leave the area as officers searched the landmark for an undisclosed object, the Daily Telegraph reported.
A Sydney Opera House employee posted an internal email to Reddit from the Head of Security, Emergency Planning and Response which said all performances and tours had been cancelled while employees were allowed to stay inside, the report said.
"Colleagues, A security threat has been received by NSW Police which they advise may involve the Opera House. Police are on site currently assessing the situation. The site has been closed to the public," the email was quoted as saying by the report.
A police operation was also carried out in Manly area of New South Wales.
