A second primary school in Sydney’s north is among four additional sites that have returned positive results for asbestos contamination.

The NSW Environment Protection Agency on Saturday confirmed Allambie Heights Public School in northern Sydney, two residential estates under construction in Sydney’s south-west and Munn Park in Millers Point have tested positive for traces of asbestos-laden mulch.

Since bonded asbestos was first found at the Rozelle Parklands in Sydney’s inner west in early January, the criminal investigation has grown into the largest in the EPA’s history.

A single piece of bonded asbestos was found in a garden bed at Allambie Heights Public School, the Department of Education confirmed.

“The garden has been cordoned off since Friday morning and work will begin as soon as possible on remediation,” the department said.

A further three sites returned positive results for asbestos but the EPA is not identifying them for privacy reasons and they are not publicly accessible.

Liverpool West Public School was shuttered on Monday due to a positive result.

Schools to be tested

Authorities have also identified four more schools for precautionary testing following inspections to seven on Friday.

They are: Domremy College in Five Dock, Edmondson Park Public School in Edmondson Park, St Michael’s Catholic Primary School in Daceyville and Trinity Catholic Primary School in Kemps Creek.

North Sydney Public School, one of the seven inspected on Friday, did not have any sign of asbestos.

Meanwhile, the  University of Sydney has been identified as a potential contamination site and will be tested this weekend.

The grounds of Sydney Olympic Park Authority are undergoing testing  after the EPA identified landscaping on a median strip as a priority location.

“At this stage, there is no sign of any asbestos in the mulch, and it is not in a highly trafficked area,” the agency said.

The number of positive sites grew to at least 32 on Saturday with more than 300 sites already tested.

About one in 10 sites have returned positive results from the testing, the EPA said.

-AAP