A school in Sydney’s north west will remain closed for a week while authorities remove an estimated 30 cubic metres of asbestos-contaminated mulch.

St Luke’s Catholic College in Marsden Park, attended by about 2,000 students, was closed last week while samples were being tested.

Those samples were confirmed to be contaminated with bonded asbestos today.

“My understanding of that school is that there was something like 30 cubic metres of mulch that was provided,” Department of Education Secretary Murat Dizdar said.

“So that’s quite an extensive amount and it’s quite widespread throughout the school.”

The NSW Environment Protection Authority (EPA) also confirmed asbestos at Penrith Christian School in Orchard Hills, taking the total number of sites in Sydney to 34.

The contaminated area at the school was not accessible to students and the school will continue with on-site learning.

EPA chief executive Tony Chappel said testing at International Grammar School in Ultimo and Westmead Christian Grammar School in Westmead came back negative for asbestos.

Precautionary testing at Sydney Olympic Park was also negative.