Almost half an Olympic swimming pool of concrete has been poured into a sinkhole left under an office building after the ground opened up near the construction site for a new tunnel.
About 1800 cubic metres of concrete poured over the weekend helped stabilise the building on West Botany Street at Rockdale before it was handed back to the owners to carry out any further repairs, Fire and Rescue NSW said in a statement on Monday.
The two-storey office building in Sydney's south partially collapsed on Friday morning.
An exclusion zone remains in place for an engineering assessment, a Transport for NSW spokesperson said in a statement on Monday.
An investigation is underway into the possible causes of the collapse near a construction site for the M6 tunnel.
"There are many complex factors that may have contributed to the subsidence," the spokesperson said.
"Tunnelling will only recommence under the impacted area after comprehensive safety and geotechnical reviews have taken place," they said.
The M6 stage one construction from Arncliffe to Kogarah is about 70 per cent complete and continues in other areas, but it is not yet known when it will recommence near the affected site, the spokesperson said.
The tunnel's construction was always going to be tough but engineers would take lessons to avoid a repeat occurrence, Premier Chris Minns said on Monday.
"It's the tunnelling part of the project that's closest to the surface and as a result of that there are major engineering challenges," he said.
Workers were evacuated on Friday, however no injures have been reported.
