Cwmcarn High School: Asbestos exposure warning
Staff and pupils at a south Wales secondary school could have been exposed to airborne asbestos, a teaching union official has said.
The 900-pupil Cwmcarn High School shut late on Friday after a structural report identified the material.
Rex Phillips of NASUWT Cymru has raised safety concerns, saying high levels of the material had been found throughout the building.
Caerphilly council said public health officials would report on Tuesday.
The announcement that the school was to close with immediate effect came on Friday afternoon.
The council said the action had been taken to safeguard the health and wellbeing of pupils and staff.
Education officials, teaching staff and engineers discussed the situation on Monday.
Mr Phillips said the problem was found when a company visited the school to carry out a survey on a boiler room.
He said the asbestos was found to be in airborne particles, with two-thirds of the school "inoperable".
"They have taken the action to close the building because of that and they have virtually got a sealed building at the school," he added.
Caerphilly council said the latest updates would be announced on its website.
It added that it was working with the school's senior leadership team and governors to explore alternative arrangements for pupils and staff, but this was unlikely to be resolved this week.
The authority said every effort was being made to accommodate pupils in years 11, 12 and 13 as a priority.
School head teacher Jacqui Peplinski has sought to reassure parents with a letter.
Asbestos expert Cenric Clement-Evans told BBC Radio Wales it was estimated that 75% of schools in Britain contained asbestos.
"At the time that schools were refurbished and rebuilt, or new-built after the war, perhaps up until the mid-70s, asbestos was seen as a fantastic material," he said.
"It provided insulation, fireproofing. It was very good and cheap for us in buildings so we used a lot of asbestos and that's why it's there."
Mr Clement-Evans added: "If it's contained, the UK government's position is that it can be managed effectively."
And he said he was campaigning for a central register in Wales to identify where asbestos is present so that it can be monitored.