Asbestos again halts work on Opera House

Workers refurbishing the Sydney Opera House have walked off the job after being exposed to asbestos for the second time in two months, their union says.

Construction has come to a stand-still at Sydney's Opera House after asbestos was again found by crews working on the $200 million refurbishments.

Electrical workers downed tools on Friday morning and refused to install cable through the iconic building after it was confirmed potentially deadly asbestos had been found, the Electrical Trades Union said in a statement.

Samples collected on Wednesday contained friable asbestos which can crumble into powder making it easier to inhale or ingest.

The discovery comes just two months after asbestos was discovered in an accessibility tunnel in the Joan Sutherland Theatre prompting a similar walk-off.

Safework NSW said they are monitoring the situation.

Building company Laind O'Rourke said construction will not resume until the site is declared safe.