Inspectors carried out an examination of the plasterwork in two classrooms on Friday and based on their findings, the school has decided to shut down the buildings.
Ardgillan College in Balbriggan to close 'immediately' after major structural issues found in school building
A spokesperson for Dublin & Dun Laoghaire Education & Training Board (DDLETB) said: " A fire safety assessment of Phase 1 was carried out and necessary works are currently being undertaken to remediate issues discovered during the assessment.
"During the course of these works, additional issues of a structural nature were identified.
"Opening up (examination of the building behind plaster work) took place in two classrooms on Friday and a consultant engineer on behalf of DDLETB discovered significant structural issues. More opening up will be required as a follow up.
"Having considered the engineer’s advice and in the interests of the health and safety of the students and staff of the school, DDLETB in consultation with the Department of Education and Skills and school management, has made the decision to close phase 1 of the school building, effective immediately."
School management is making "immediate arrangements" to accommodate up to 200 students displaced by the closure and its understood they will contact parents and guardians once those arrangements are finalised.
In a statement released on Sunday evening, they said: "For the purposes of clarification, all pupils should attend Ardgillan Community College as normal tomorrow (Monday) and the week ahead, with the exception of Transition Year students, approximately 90 of whom have been asked not to attend in order to free up school capacity for the week ahead."
The spokesperson added that Phase 2 of the building, which was built in 2015 "remains unaffected".
Just last week Ardgillan Community College was forced to shut down after a student there posted a picture of a gun on Instagram and threatened to 'shoot up' his school.
The school was closed for one day and 16-year-old male student was arrested in connection with the incident.
However he was later released without charge.
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