No more asbestos-contaminated mulch has been found in Queensland's southeast with investigators now focusing on the origins of the positive result at one waste facility.
Two friable asbestos fragments - about 1.5mm by 3mm - were discovered in a compost stockpile at waste company NuGrow's Ipswich site west of Brisbane in the wake of the Sydney outbreak.
NuGrow Ipswich is the only site to return a positive result out of the 23 landfill operations, transfer stations, landscape suppliers, composters, and mulch suppliers tested, the Department of Environment, Science and Innovation (DESI) confirmed on Friday.
"Today's results have shown us that the risk of asbestos contamination in soil, mulch, and compost in Queensland is low, and we hope that these results bring some comfort to the community," DESI director Brad Wirth said in a statement.
But authorities are now expanding the search outside the southeast with a further six sites inspected so far.
The potentially tainted soil from the Ipswich waste facility was taken to nine sites, including six schools, in the past 30 days.
A Greenbank dog park is also among the public sites being investigated.
Initially, there were concerns up to 25 sites were supplied with the potentially hazardous material but authorities are continuing to narrow down the number.
More sites may be listed as authorities investigate the supply chain.
Authorities are cautiously optimistic that the chance of an outbreak has been contained after a singular positive result.
"Given the nature of its use and the extremely small size of the one positive sample found, the risk to the public is low, but we will continue to take no chances," Workplace Health and Safety Queensland regulator Peter McKay said.
But investigators are now honing in on the Ipswich site, deploying air quality monitoring to the Swanbank area to test for the presence of any airborne asbestos.
NuGrow is also required to tell DESI about the potential sources of the asbestos.
"While the source of asbestos at the NuGrow site is yet to be determined, it's timely to remind waste operators of their obligations to properly inspect incoming waste for asbestos and to have procedures in place to segregate and manage any asbestos received," Mr Wirth said.
The waste company will be investigated as to whether it complied with its environmental responsibilities.
NuGrow said in a statement Thursday it was working closely with authorities.
"The safety of NuGrow's staff, clients and the broader community is our utmost priority at this time, as always," it said.
