On Wednesday night, parents gathered for answers at the Harrison School in Gungahlin, where asbestos was discovered a fortnight ago in garden beds throughout the large public school. A week later, and just a few hundred metres away, more non-friable asbestos was unearthed in a garden bed in the car park of Mother Teresa Catholic Primary School.

Fences still encircle both schools to keep all garden beds out of bounds, but the bulk of works to remove the asbestos at Harrison School will not occur until the school holidays, the education directorate confirmed.

Asbestos assessor John Robson, who tested the samples, said the material was abestos cement sheeting which had been crushed up and scattered in low quantities throughout the garden bed fill.

"It came from a recycling plant," he said.

In Mr Robson's final report for the Harrison School, handed down on Wednesday, 55 samples were tested but not all garden beds were found to contain asbestos. The majority of the material was discovered in those throughout the senior school.

David Matthews from the ACT education directorate said there was no reason to believe further testing was needed anywhere else on site, such as the oval.

While asbestos fibres were likely released during the recycling process, as the material was broken down into chunks about the size of a 50 cent coin, Mr Robson said most fibres would have remained behind at the plant.

"This stuff, you can rub it in your hand and not release the fibres," he said.

Non-friable or bonded asbestos - meaning it cannot be pulverised, crumbled or reduced to power by hand - does not typically release fibres.

If breathed in, asbestos fibres can lead to a number of serious diseases, including cancer, but ACT chief health officer Paul Kelly told parents the risk in this case was extremely low.

"This is not Mr Fluffy," Dr Kelly said. "This is a very different situation."

While children had been known to play in the garden beds, Dr Kelly said only a significant disturbance such as the use of power drills would be expected to degrade the asbestos.

WorkSafe ACT commissioner Greg Jones said investigators were "100 per cent confident" that the site had not previously been contaminated with asbestos before the Harrison School was built.

That left records from landscaping works over the school's ten-year history for investigators to narrow in on who had brought it on site and which recycling facility had supplied it to them.

"We're going absolutely flat chat on this...and we're making good progress even wading through that level of documentation, we're hoping to have narrowed down the time-frame [some time] next week," Mr Jones said.

"If there was a lot of building being done at the time, [the material] could have even come from interstate...we don't know how big this is."

Whether or not other sites or schools in Canberra had been supplied with the same material was a key question for the investigation, he said. WorkSafe is also working with the Catholic Education Office and Mother Teresa Primary, where testing has also finished.

Once a parent raised concerns about the garden beds at Harrison, an assessor was brought in to carry out testing the next day, "a perfect response" according to Mr Jones.

All garden beds at the school would be removed, whether they contained asbestos or not, Mr Matthews said, adding the directorate aimed to replace them completely by first term next year.

But the safest way to remove the abestos itself was out of hours - on weekends and during the school holidays. Mr Jones said teams would priortise contaminated garden beds and then those near the car park, where fencing was already causing headaches during the morning and afternoon rush.

Mr Matthews said the government was also setting up a dedicated contact phone number and encouraged anyone with a connection to the school and concerns about the discovery to get in touch.

While the government was not actively tracking down past staff and students of the school to notify them, Mr Matthews said this was not an attempt to keep the issue quiet but rather to ensure the response was proportional.

"We don't want to unduly alarm people," he said.

People could register with the national asbestos exposure register, Dr Kelly said, but this was not required at this time due to the relatively low risk.

Asbestos management works were also carried out over the weekend at Arawang Primary School, but an education directorate spokeswoman confirmed these were "business-as-usual" works.

"[They involved] minor treatments to known non-friable asbestos materials [and] the school community is aware of the...management plan in place," she said.

"These works have no connection to Harrison School."

Parents concerned their children had inadvertantly taken home material from the Harrison School garden beds were advised to double-bag the item and return it to the school for removal. Anyone with health concerns should see a doctor.

More information on asbestos in the ACT can be found at asbestos.act.gov.au