She said the Ministry was reassured by the results, however more tests will be carried out before the school is reopened.
Mr McPherson said the majority of the demolition work was carried out during the school holidays, and they had expected it to be finished before school resumed.
"Before the school reopened on Monday we sought a number of assurances from the project team that the site was safe and that they had complied with their removal obligations, we got those assurances and no reason to disbelieve them.''
Mr McPherson said he had been taking calls from concerned parents today.
"The questions that our parents have been asking us are the questions we are asking of the contractors and the Ministry,'' he said.
"We've got to work through a whole lot of processes to get the right information to be able to get that to our parents.''
Work Safe NZ has given contractors the green light to remove the demolished material from the school, and Mr McPherson expected that to be completed tomorrow.
The school will be swabbed and air quality tests will be carried out to ensure no trace of asbestos is found before it is reopened.
He said he hoped students would be able to return to school on Monday, however plans were in motion for a alternative classrooms for the students if the school must remain closed longer.
"We're not prepared to reopen the school until we're totally satisfied,'' he said.
The Ministry of Education will be investigating the management of the work site.