The Sydney Opera House has launched an independent investigation after more than 50 workers were potentially exposed to deadly asbestos for almost a week during renovations.
Workers for the company tasked with the $200 million renovations, Laing O'Rourke, located the asbestos during the construction of an accessibility tunnel alongside the Joan Sutherland Theatre, a Sydney Opera House spokesman confirmed on Thursday.
The Electrical Trades Union has accused the builder of not observing safety protocols after the discovery on Monday July 24. Some workers downed tools as a result.
The Opera House says the asbestos has now been removed and Laing O'Rourke have obtained a clearance certificate with the site declared safe.
The spokeswoman said the Opera House had launched an independent investigation into the incident to ensure the building's safety procedures were being followed.
"We work constantly to ensure everyone who works at or visits the site is safe," she said.
"It is our highest priority."
ETU NSW assistant secretary Justin Page says it's "absolutely shocking" that despite the risk being completely foreseeable management failed to put proper safety precautions in place to protect workers.
Mr Page on Thursday told AAP an agreement between the union and building management was made on Wednesday for an independent hygienist to inspect the site and for a separate meeting for workers to discuss their concerns.
However, the independent hygienist was refused access to the site on Thursday by Laing O'Rourke, the union says.
It says renovations won't resume until the independent hygienist is given access.
Most work is continuing on the project, the Opera House spokeswoman said.
"But we are aware that a number of Laing O'Rourke subcontractors, represented by the unions, have stopped work."
The Asbestos Safety and Eradication Agency has called for an urgent program to remove high-risk asbestos from all buildings Australia-wide.
Comment has been sought from Laing O'Rourke.